Projection device and image correction method

ABSTRACT

A projection device includes a correction unit that corrects a trapezoidal distortion of a projection image projected onto a projection medium in accordance with a projection angle derived by a projection angle deriving unit, and the correction unit sets a correction amount for the trapezoidal distortion of a case where the derived projection angle is changed within a range larger than a first predetermined angle determined based on the projection direction toward a boundary between a first projection face and a second projection face and smaller than a second predetermined angle determined based on the projection direction toward the boundary to be the correction amount for the trapezoidal distortion at one of the first predetermined angle and the second predetermined angle or less.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Application No.PCT/JP2013/063462, filed on May 14, 2013 which claims the benefit ofpriority of the prior Japanese Patent Application No. 2012-115072, filedon May 18, 2012, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection device and an imagecorrection method.

2. Description of the Related Art

A projection device such as a projector device is known which drivesdisplay elements based on an input image signal and projects an imagerelating to the image signal on a projection face of a projection mediumsuch as a screen or a wall face. In such a projection device, in a casewhere a projection image is projected not in a state in which an opticalaxis of a projection lens is perpendicular to the projection face but ina state in which the optical axis of the projection lens is inclinedwith respect to the projection face, a problem of a so-calledtrapezoidal distortion in which a projection image projected in anoriginally approximate rectangular shape is displayed to be distorted ina trapezoidal shape on the projection face occurs.

Accordingly, conventionally, by performing a trapezoidal correction(keystone correction) for converting an image that is a projectiontarget into a trapezoidal shape formed in a direction opposite to thetrapezoidal distortion occurring in the projection image displayed onthe projection face, a projection image having an approximatelyrectangular shape without any distortion is displayed on the projectionface.

For example, in Japanese Patent Application Laid-open No. 2004-77545, atechnology for projecting an excellent video for which a trapezoidaldistortion correction has been appropriately performed onto a projectionface in a projector also in a case where the projection face is either awall face or a ceiling is disclosed.

More specifically, in Japanese Patent Application Laid-open No.2004-77545, a technology is disclosed in which, in a case where a videois projected while moving the video in the vertical direction, when aninclined angle from a reference position, which relates to the verticaldirection, of an inclining mechanism unit supporting a video projectionmechanism unit projecting the video to be rotatable in the verticaldirection becomes a predetermined inclined angle set in advance, thedegree of correction at the time of performing a trapezoidal correctionfor video data corresponding to a video is changed by reversing theupper side and the lower side of the trapezoid.

In addition, in Japanese Patent Application Laid-open No. 2004-77545, atechnology is disclosed in which, in a case where a video is projectedwhile being moved in the horizontal direction, when a displacement angledisplaced from the reference position, which relates to the horizontaldirection, of a rotation mechanism unit that supports the videoprojection mechanism unit projecting a video to be rotatable in thehorizontal direction becomes a predetermined displacement angle set inadvance, the degree of correction at the time of performing atrapezoidal correction of video data corresponding to a video is changedby reverting the left side and the right side of the trapezoid.

Meanwhile, in Japanese Patent Application Laid-open No. 2004-77545described above, in a case where the projection position on a projectionmedium is moved while the video is continued to be projected, the kindof the trapezoidal correction performed on each corner of the projectionmedium and the kind of video to be projected are not disclosed.

In other words, for example, when a video is continuously projectedwhile the projection position is changed from the front wall portion ofthe projection medium to the ceiling portion, in a case where a cornerof the front wall portion and the ceiling portion is included in theprojection range of the projected video, the kind of the trapezoidalcorrection to be performed and the like are not disclosed. The same istrue of the case of a corner of the front wall portion and the side wallportion. Only it is disclosed that the degree of a correction for theprojected video is switched between before and after a predetermineddisplacement angle set in advance in a non-continuous manner.

Thus, in a case where the projection position on the projection mediumis changed while the projection of the video is continued, according tothe technology disclosed in Japanese Patent Application Laid-open No.2004-77545 described above, in a case where the projected video ispositioned at the corner (for example, a corner of the front wallportion and the side wall portion or a corner of the front wall portionand the ceiling portion) of the projection medium, a problem in that theshape of the projected video changes in a non-continuous manner beforeand after the above-described predetermined displacement angle set inadvance is supposed to occur.

For example, in a case where the projection position of the video ischanged from the front wall portion to the ceiling portion, the videopositioned at the corner is projected for up to the predetermineddisplacement angle such that a portion projected to the front wallportion has a rectangular shape, and a portion projected to the ceilingportion with the corner formed as the boundary has a trapezoidal shape.Then, after the predetermined displacement angle, a video is projectedsuch that a portion projected to the front wall portion has atrapezoidal shape, and a portion projected to the ceiling portion withthe corner formed as the boundary has a rectangular shape. In otherwords, between before and after the predetermined displacement angle,the shape of the projected video changes in a non-continuous manner.

In addition, in a case where the projection image reciprocates over thecorner of the projection medium or in a case where the movement of theprojection image is stopped at the corner limit, the forward/backwardconversion of the trapezoidal correction is repeatedly performed, andthe shape of the projected video repeatedly changes in a non-continuousmanner in accordance with the repeated conversion, and accordingly, theoccurrence of a problem in that the projection image becomes unstablemay be supposed.

As above, according to the technology disclosed in Japanese PatentApplication Laid-open No. 2004-77545 described above, at the corner oftwo projection faces of the projection medium such as a wall face and aceiling face lined up to have a predetermined angle therebetween, thatis, at the boundary between two projection faces, the occurrence of aproblem in that it is difficult to project a smooth and stableprojection image that is easily viewable for an observer is supposed.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

There is provided a projection device that includes a projection unitthat converts input image data into light and projects converted lightwith a predetermined view angle as a projection image onto a projectionmedium configured by a first projection face and a second projectionface lined up to have a predetermined angle therebetween; a projectiondirection changing unit that changes a projection direction of theprojection unit from a first projection direction up to a secondprojection direction; a projection angle deriving unit that derives aprojection angle of the projection unit in the projection directionchanged by the projection direction changing unit; and a correction unitthat corrects a trapezoidal distortion of the projection image projectedonto the projection medium in accordance with the projection anglederived by the projection angle deriving unit, and the correction unitsets a correction amount for the trapezoidal distortion of a case wherethe derived projection angle is changed within a range larger than afirst predetermined angle determined based on the projection directiontoward a boundary between the first projection face and the secondprojection face and smaller than a second predetermined angle determinedbased on the projection direction toward the boundary to be thecorrection amount for the trapezoidal distortion at one of the firstpredetermined angle and the second predetermined angle or less.

There is also provided an image correction method that includesconverting input image data into light and projecting converted lightwith a predetermined view angle as a projection image onto a projectionmedium configured by a first projection face and a second projectionface lined up to have a predetermined angle therebetween using aprojection unit; changing a projection direction of the projection unitfrom a first projection direction up to a second projection direction;deriving a projection angle of the projection unit in the projectiondirection changed in the changing of a projection direction; andcorrecting a trapezoidal distortion of the projection image projectedonto the projection medium in accordance with the projection anglederived in the deriving of a projection angle, and in the correcting ofa trapezoidal distortion, a correction amount for the trapezoidaldistortion of a case where the derived projection angle is changedwithin a range larger than a first predetermined angle determined basedon the projection direction toward a boundary between the firstprojection face and the second projection face and smaller than a secondpredetermined angle determined based on the projection direction towardthe boundary is set to be the correction amount for the trapezoidaldistortion at one of the first predetermined angle and the secondpredetermined angle or less. The above and other objects, features,advantages and technical and industrial significance of this inventionwill be better understood by reading the following detailed descriptionof presently preferred embodiments of the invention, when considered inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram that illustrates an example of theexternal view of a projector device according to a first embodiment;

FIG. 1B is a schematic diagram that illustrates an example of theexternal view of the projector device according to the first embodiment;

FIG. 2A is a schematic diagram that illustrates an example of theconfiguration for performing rotary drive of a drum unit according tothe first embodiment;

FIG. 2B is a schematic diagram that illustrates an example of theconfiguration for performing rotary drive of the drum unit according tothe first embodiment;

FIG. 3 is a schematic diagram that illustrates each posture of the drumunit according to the first embodiment;

FIG. 4 is a block diagram that illustrates the functional configurationof the projector device according to the first embodiment;

FIG. 5 is a conceptual diagram that illustrates a cutting out process ofimage data stored in a memory according to the first embodiment;

FIG. 6 is a schematic diagram that illustrates an example of designationof a cut out area of a case where the drum unit according to the firstembodiment is located at an initial position;

FIG. 7 is a schematic diagram that illustrates setting of a cut out areafor a projection angle θ according to the first embodiment;

FIG. 8 is a schematic diagram that illustrates designation of a cut outarea of a case where optical zooming is performed in accordance with thefirst embodiment;

FIG. 9 is a schematic diagram that illustrates a case where an offset isgiven for a projection position of an image according to the firstembodiment;

FIG. 10 is a schematic diagram that illustrates an image projected to aperpendicular face according to the first embodiment;

FIG. 11 is a schematic diagram that illustrates an image projected to aperpendicular face according to the first embodiment;

FIG. 12 is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 13 is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 14A is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 14B is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 14C is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 15A is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 15B is a schematic diagram that illustrates access control of amemory according to the first embodiment;

FIG. 16 is a diagram that illustrates a projector device 1 according tothe first embodiment and major projection directions of a projectionlens 12 in a case where a floor face, a wall face, and a ceiling areused as projection faces;

FIG. 17A is a diagram that illustrates a keystone correction accordingto the first embodiment that is performed in a case where image data isprojected onto a projection face illustrated in FIG. 16;

FIG. 17B is a diagram that illustrates a keystone correction accordingto the first embodiment that is performed in a case where image data isprojected onto the projection face illustrated in FIG. 16;

FIG. 18 is a diagram that illustrates major projection directions andprojection angles of the projection face according to the firstembodiment;

FIG. 19 is a graph that illustrates a relation between a projectionangle and a correction coefficient according to the first embodiment;

FIG. 20 is a diagram that illustrates the calculation of the correctioncoefficient according to the first embodiment;

FIG. 21 is a diagram that illustrates the calculation of lengths oflines from the upper side to the lower side according to the firstembodiment;

FIG. 22 is a flowchart that illustrates the sequence of an imageprojection process according to the first embodiment;

FIG. 23 is a diagram that illustrates major projection directions andprojection angles of a projection face according to a first modifiedexample relating to the first embodiment;

FIG. 24 is a graph that illustrates a relation between a projectionangle and a correction coefficient according to the first modifiedexample relating to the first embodiment;

FIG. 25 is a diagram that illustrates an example of an external view ofa projector device according to a second embodiment;

FIG. 26 illustrates an example of the external view of a base accordingto the second embodiment;

FIG. 27 is a diagram that illustrates a turntable according to thesecond embodiment seen from the rear face side;

FIG. 28A is a diagram that illustrates an example of a relation betweeninput image data and projection image data acquired by cutting out theinput image data according to the second embodiment;

FIG. 28B is a diagram that illustrates an example of a relation betweeninput image data and projection image data acquired by cutting out theinput image data according to the second embodiment;

FIG. 28C is a diagram that illustrates an example of a relation betweeninput image data and projection image data acquired by cutting out theinput image data according to the second embodiment;

FIG. 29 is a diagram that illustrates the projector device and majorprojection directions of a projection lens according to the secondembodiment in a case where two wall faces are used as the projectionfaces;

FIG. 30A is a diagram that illustrates a keystone correction accordingto the second embodiment in a case where image data is projected ontothe projection faces that are two wall faces;

FIG. 30B is a diagram that illustrates a keystone correction accordingto the second embodiment in a case where image data is projected ontothe projection faces that are two wall faces;

FIG. 30C is a diagram that illustrates a keystone correction accordingto the second embodiment in a case where image data is projected ontothe projection faces that are two wall faces;

FIG. 31A is a diagram that illustrates a case where the keystonecorrection is not performed;

FIG. 31B is a diagram that illustrates a case where the keystonecorrection is not performed;

FIG. 32A is a diagram that illustrates a conventional keystonecorrection;

FIG. 32B is a diagram that illustrates a conventional keystonecorrection; and

FIG. 33 is a graph that illustrates a relation among a projection angle,a view angle, and a correction coefficient according to a conventionaltechnology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, projection devices and image correction methods accordingto embodiments will be described in detail with reference to theaccompanying drawings. Specific numerical values, externalconfigurations, and the like represented in the embodiments are merelyexamples for easy understanding of the present invention but are not forthe purpose of limiting the present invention unless otherwisementioned. In addition, elements not directly relating to the presentinvention are not described in detail and are not presented in thedrawings.

First Embodiment External View of Projection Device

FIGS. 1A and 1B are schematic diagrams that illustrate an example of theexternal views of a projection device (projector device) 1 according toa first embodiment. FIG. 1A is a perspective view of the projectordevice 1 viewed from a first face side on which an operation unit isdisposed, and FIG. 1B is a perspective view of the projector device 1viewed from a second face side that is a side facing the operation unit.The projector device 1 includes a drum unit 10 and a base 20. The drumunit 10 is a rotor that is driven to be rotatable with respect to thebase 20. In addition, the base 20 includes a support portion supportingthe drum unit 10 to be rotatable and a circuit unit performing variouscontrol operations such as rotation driving control of the drum unit 10and image processing control.

The drum unit 10 is supported to be rotatable by a rotation shaft, whichis not illustrated in the figure, that is disposed on the inner side ofside plate portions 21 a and 21 b that are parts of the base 20 and isconfigured by a bearing and the like. Inside the drum unit 10, a lightsource, a display element that modulates light emitted from the lightsource based on image data, a drive circuit that drives the displayelement, an optical engine unit that includes an optical systemprojecting the light modulated by the display element to the outside,and a cooling means configured by a fan and the like used for coolingthe light source and the like are disposed.

In the drum unit 10, window portions 11 and 13 are disposed. The windowportion 11 is disposed such that light projected from a projection lens12 of the optical system described above is emitted to the outside. Inthe window portion 13, a distance sensor deriving a distance up to aprojection medium, for example, using an infrared ray, an ultrasonicwave, or the like is disposed. In addition, the drum unit 10 includes anintake/exhaust hole 22 a that performs air in-taking/exhausting for heatrejection using a fan.

Inside the base 20, various substrates of the circuit unit, a powersupply unit, a drive unit used for driving the drum unit 10 to berotated, and the like are disposed. The rotary drive of the drum unit 10that is performed by this drive unit will be described later. On thefirst face side of the base 20, an operation unit 14 used for inputtingvarious operations for controlling the projector device 1 and areception unit 15 that receives a signal transmitted from a remotecontrol commander not illustrated in the figure when the projectordevice 1 is remotely controlled by a user using the remote controlcommander are disposed. The operation unit 14 includes various operatorsreceiving user's operation inputs, a display unit used for displayingthe state of the projector device 1, and the like.

On the first face side and the second face side of the base 20, theintake/exhaust holes 16 a and 16 b are respectively disposed. Thus, evenin a case where the intake/exhaust hole 22 a of the drum unit 10 that isdriven to be rotated takes a posture toward the base 20 side, airin-taking or air exhaust can be performed so as not to decrease therejection efficiency of the inside of the drum unit 10. In addition, theintake/exhaust hole 17 disposed on the side face of the casing performsair in-taking and air exhaust for heat rejection of the circuit unit.

Rotary Drive of Drum Unit

FIGS. 2A and 2B are diagrams that illustrate the rotary drive of thedrum unit 10 that is performed by a drive unit 32 disposed in the base20. FIG. 2A is a diagram that illustrates the configuration of a drum 30in a state in which a cover and the like of the drum unit 10 are removedand the drive unit 32 disposed in the base 20. In the drum 30, a windowportion 34 corresponding to the window portion 11 described above and awindow portion 33 corresponding to the window portion 13 are disposed.The drum 30 includes a rotation shaft 36 and is attached to a bearing 37using bearings disposed in support portions 31 a and 31 b to be drivento rotate by the rotation shaft 36.

On one face of the drum 30, a gear 35 is disposed on the circumference.The drum 30 is driven to be rotated through the gear 35 by the driveunit 32 disposed in the support portion 31 b. Here, protrusions 46 a and46 b disposed in the inner circumference portion of the gear 35 aredisposed so as to detect a start point and an end point at the time ofthe rotation operation of the drum 30.

FIG. 2B is an enlarged diagram that illustrates the configuration of thedrum 30 and the drive unit 32 disposed in the base 20 in more detail.The drive unit 32 includes a motor 40 and a gear group including a wormgear 41 that is directly driven by the rotation shaft of the motor 40,gears 42 a and 42 b that transfer rotation according to the worm gear41, and a gear 43 that transfers the rotation transferred from the gear42 b to the gear 35 of the drum 30. By transferring the rotation of themotor 40 to the gear 35 using the gear group, the drum 30 can be rotatedin accordance with the rotation of the motor 40. As the motor 40, forexample, a stepping motor performing rotation control for eachpredetermined angle using a drive pulse may be used.

In addition, photo interrupters 51 a and 51 b are disposed on thesupport portion 31 b. The photo interrupters 51 a and 51 b respectivelydetect the protrusions 46 b and 46 a disposed in the inner circumferenceportion of the gear 35. Output signals of the photo interrupters 51 aand 51 b are supplied to a rotation control unit 104 to be describedlater. In the embodiment, by detecting the protrusion 46 b using thephoto interrupter 51 a, the rotation control unit 104 determines thatthe posture of the drum 30 is a posture arriving at an end point of therotation operation. In addition, by detecting the protrusion 46 a usingthe photo interrupter 51 b, the rotation control unit 104 determinesthat the posture of the drum 30 is a posture arriving at a start pointof the rotation operation.

Hereinafter, a direction in which the drum 30 rotates from a position atwhich the protrusion 46 a is detected by the photo interrupter 51 b to aposition at which the protrusion 46 b is detected by the photointerrupter 51 a through a longer arc in the circumference of the drum30 will be represented as a forward direction. In other words, therotation angle of the drum 30 increases toward the forward direction.

In addition, the photo interrupters 51 a and 51 b and the protrusions 46a and 46 b are arranged such that an angle formed with the rotationshaft 36 is 270° between the detection position at which the photointerrupter 51 b detects the protrusion 46 a and the detection positionat which the photo interrupter 51 a detects the protrusion 46 b.

For example, in a case where a stepping motor is used as the motor 40,by specifying the posture of the drum 30 based on timing at which theprotrusion 46 a is detected by the photo interrupter 51 b and the numberof drive pulses used for driving the motor 40, a projection angleaccording to the projection lens 12 can be acquired.

Here, the motor 40 is not limited to the stepping motor but, forexample, a DC motor may be used. In such a case, for example, asillustrated in FIG. 2B, a code wheel 44 rotating together with the gear43 on the same shaft as that of the gear 43 is disposed, and photoreflectors 50 a and 50 b are disposed in the support portion 31 b,whereby a rotary encoder is configured.

In the code wheel 44, for example, a transmission unit 45 a and areflection unit 45 b having phases changing in the radial direction aredisposed. By receiving reflected light having each phase from the codewheel 44 using the photo reflectors 50 a and 50 b, the rotation speedand the rotation direction of the gear 43 can be detected. Then, basedon the rotation speed and the rotation direction of the gear 43 thathave been detected, the rotation speed and the rotation direction of thedrum 30 are derived. Based on the rotation speed and the rotationdirection of the drum 30 that have been derived and a result of thedetection of the protrusion 46 b that is performed by the photointerrupter 51 a, the posture of the drum 30 is specified, whereby theprojection angle according to the projection lens 12 can be acquired.

In the configuration as described above, a state in which the projectiondirection according to the projection lens 12 is in the verticaldirection, and the projection lens 12 is completely hidden by the base20 will be referred to as a housed state (or housing posture). FIG. 3 isa schematic diagram that illustrates each posture of the drum unit 10.In FIG. 3, State 500 illustrates the appearance of the drum unit 10 thatis in the housed state. In the embodiment, the protrusion 46 a isdetected by the photo interrupter 51 b in the housed state, and it isdetermined that the drum 30 arrives at the start point of the rotationoperation by the rotation control unit 104 to be described later.

Hereinafter, unless otherwise mentioned, the “direction of the drum unit10” and the “angle of the drum unit 10” have the same meanings as the“projection direction according to the projection lens 12” and the“projection angle according to the projection lens 12”.

For example, when the projector device 1 is started up, the drive unit32 starts to rotate the drum unit 10 such that the projection directionaccording to the projection lens 12 faces the above-described first faceside. Thereafter, the drum unit 10, for example, is assumed to rotate upto a position at which the direction of the drum unit 10, in otherwords, the projection direction according to the projection lens 12 ishorizontal on the first face side and temporarily stop. The projectionangle of the projection lens 12 of a case where the projection directionaccording to the projection lens 12 is horizontal on the first face sideis defined as a projection angle of 0°. In FIG. 3, State 501 illustratesthe appearance of the posture of the drum unit 10 (projection lens 12)when the projection angle is 0°. Hereinafter, the posture of the drumunit 10 (projection lens 12) at which the projection angle is θ withrespect to the posture having a projection angle of 0° used as thereference will be referred to as a θ posture. In addition, the state ofthe posture having a projection angle of 0° (in other words, a 0°posture) will be referred to as an initial state.

For example, at the 0° posture, it is assumed that image data is input,and the light source is turned on. In the drum unit 10, light emittedfrom the light source is modulated based on the image data by thedisplay element driven by the drive circuit and is incident to theoptical system. Then, the light modulated based on the image data isprojected from the projection lens 12 in a horizontal direction and isemitted to the projection face of the projection medium such as a screenor a wall face.

By operating the operation unit 14 and the like, the user can rotate thedrum unit 10 around the rotation shaft 36 as its center while projectionis performed from the projection lens 12 based on the image data. Forexample, by getting the rotation angle to be 90° (90° posture) byrotating the drum unit 10 from the 0° posture in the forward direction,light emitted from the projection lens 12 can be projected verticallyupwardly with respect to the bottom face of the base 20. In FIG. 3,State 502 illustrates the appearance of the drum unit 10 at the posturehaving a projection angle θ of 90°, in other words, a 90° posture.

The drum unit 10 can be rotated further in the forward direction fromthe 90° posture. In such a case, the projection direction of theprojection lens 12 changes from the vertically upward direction withrespect to the bottom face of the base 20 to the direction of the secondface side. In FIG. 3, State 503 illustrates an appearance acquired whena posture having a projection angle θ of 180°, in other words, a 180°posture is formed as the drum unit 10 further rotates in the forwarddirection from the 90° posture of State 502. In the projector device 1according to this embodiment, the protrusion 46 b is detected by thephoto interrupter 51 a in this 180° posture, and it is determined thatthe drum has arrived at the end point of the rotation operation of thedrum 30 by the rotation control unit 104 to be described later.

As will be described later, the projector device 1 according to thisembodiment rotates the drum unit 10, for example, as illustrated inStates 501 to 503, while an image is projected, whereby the projectionarea in the image data can be changed (moved) in accordance with aprojection angle according to the projection lens 12. In this way, acontent of a projected image and a change in the projection position ofthe projected image on the projection medium and a content and a changein the position of an image area cut out as an image to be projectedfrom the whole image area relating to input image data can be associatedwith each other. Accordingly, a user can intuitively recognize aprojected area of the whole image area relating to the input image databased on the position of the projected image on the projection mediumand can intuitively perform an operation of changing the content of theprojected image.

In addition, the optical system includes an optical zoom mechanism andcan enlarge or reduce the size at the time of projecting a projectionimage to the projection medium by operating the operation unit 14.Hereinafter, the enlarging or reducing of the size at the time ofprojecting the projection image to the projection medium according tothe optical system may be simply referred to as “zooming”. For example,in a case where the optical system performs zooming, the projectionimage is enlarged or reduced with respect to the optical axis of theoptical system as its center at the time point of performing zooming.

When the user ends the projection of the projection image using theprojector device 1 and stops the projector device 1 by performing anoperation for instructing the operation unit 14 to stop the projectordevice 1, first, rotation control is performed such that the drum unit10 is returned to be in the housed state. When the drum unit 10 ispositioned toward the vertical direction, and the return of the drumunit 10 into the housed state is detected, the light source is turnedoff, and, after a predetermined time required for cooling the lightsource, the power is turned off. By turning the power off after the drumunit 10 is positioned toward the vertical direction, the projection lens12 can be prevented from getting dirty when the projection lend is notused.

Functional Configuration of Projector Device 1

Next, a configuration for realizing each function or operation of theprojector device 1 according to this embodiment, as described above,will be described. FIG. 4 is a block diagram that illustrates thefunctional configuration of the projector device 1.

As illustrated in FIG. 4, the projector device 1 mainly includes: anoptical engine unit 110, a rotation mechanism unit 105; a rotationcontrol unit 104; a view angle control unit 106; an image control unit103; an image processing unit 102; an image cut-out unit 100; a keystonecorrection unit 108; a keystone adjustment unit 107; a registration unit118; an input control unit 119; a memory 101; a boundary storage unit109; and an operation unit 14.

Here, the optical engine unit 110 is disposed inside the drum unit 10.In addition, the rotation control unit 104, the view angle control unit106, the image control unit 103, the image processing unit 102, theimage cut-out unit 100, the keystone correction unit 108, the keystoneadjustment unit 107, the memory 101, the boundary storage unit 109, theregistration unit 118, the input control unit 119 are mounted on asubstrate of the base 20 as circuit units.

The optical engine unit 110 includes a light source 111, a displayelement 114, and a projection lens 12. The light source 111, forexample, includes three light emitting diodes (LEDs) respectivelyemitting red (R) light, green (G) light, and blue (B) light. Luminousfluxes of colors RGB that are emitted from the light source 111irradiate the display element 114 through an optical system notillustrated in the figure.

In description presented below, the display element 114 is assumed to bea transmission-type liquid crystal display device and, for example, tohave a size of horizontal 1280 pixels×vertical 800 pixels. However, thesize of the display element 114 is not limited to this example. Thedisplay element 114 is driven by a drive circuit not illustrated in thefigure and modulates luminous fluxes of the colors RGB based on imagedata and emits the modulated luminous fluxes. The luminous fluxes of thecolors RGB that are emitted from the display element 114 and aremodulated based on the image data are incident to the projection lens 12through the optical system not illustrated in the figure and areprojected to the outside of the projector device 1.

In addition, the display element 114, for example, may be configured bya reflection-type liquid crystal display device using liquid crystal onsilicon (LCOS) or a digital micromirror device (DMD). In such a case,the projector device is configured by an optical system and a drivecircuit that correspond to the used display element.

The projection lens 12 includes a plurality of lenses that are combinedtogether and a lens driving unit that drives the lenses according to acontrol signal. For example, the lens driving unit drives a lensincluded in the projection lens 12 based on a result of distancemeasurement that is acquired based on an output signal output from adistance sensor disposed in the window portion 13, thereby performingfocus control. In addition, the lens driving unit changes the view angleby driving the lens in accordance with a zoom instruction supplied fromthe view angle control unit 106 to be described later, therebycontrolling the optical zoom.

As described above, the optical engine unit 110 is disposed inside thedrum unit 10 that can be rotated by 360° by the rotation mechanism unit105. The rotation mechanism unit 105 includes the drive unit 32 and thegear 35 that is a configuration of the drum unit 10 side described withreference to FIGS. 2A and 2B, and rotates the drum unit 10 in apredetermined manner using the rotation of the motor 40. In other words,the projection direction of the projection lens 12 is changed by therotation mechanism unit 105.

Input image data 120 of a still image or a moving image is input to theprojector device 1 and is supplied to the image cut-out unit 100. Theimage cut-out unit 100 stores the supplied input image data 120 in thememory 101. The memory 101 stores the input image data 120 in units ofimages. In other words, for each still image in a case where the inputimage data 120 is still image data, or for each frame image configuringmoving image data in a case where the input image data 120 is the movingimage data, corresponding data is stored. The memory 101, for example,is in compliance with the standards of digital high vision broadcastingand can store one or a plurality of frame images of 1920 pixels×1080pixels. The image cut-out unit 100 cuts out (extracts) an image areadesignated by the image control unit 103 from the whole area of theframe image relating to the input image data 120 that is stored in thememory 101 and outputs the cut image area as image data.

In addition, it is preferable that the size of the input image data 120is shaped in advance into a size corresponding to the storage unit ofthe image data in the memory 101, and resultant input image data isinput to the projector device 1. In this example, the size of the inputimage data 120 is shaped in advance into 1920 pixels×1080 pixels, andresultant input image is input to the projector device 1. However, theconfiguration is not limited thereto, but an image shaping unit thatshapes the input image data 120 input with an arbitrary size into imagedata of a size of 1920 pixels and 1080 pixels may be disposed in a priorstage of the image cut-out unit 100 in the projector device 1.

The image data output from the image cut-out unit 100 is supplied to theimage processing unit 102. The image processing unit 102, for example,by using a memory not illustrated in the figure, performs imageprocessing for the supplied image data. The image processing unit 102outputs the image data for which the image processing has been performedbased on timing represented in a vertical synchronization signal 124supplied from a timing generator not illustrated in the figure. Theimage processing unit 102, for example, performs a size convertingprocess for the image data supplied from the image cut-out unit 100 suchthat the size matches the size of the display element 114. In addition,other than the process, the image processing unit 102 may performvarious kinds of image processing. For example, the image processingunit 102 may perform the size converting process for the image datausing a general linear transformation process. In addition, in a casewhere the size of the image data supplied from the image cut-out unit100 matches the size of the display element 114, the image data may bedirectly output.

In addition, by performing interpolation (over sampling) with the aspectratio of the image being maintained to be constant, a part or the wholeof the image may be enlarged through an interpolation filter having apredetermined characteristic, in order to extract an aliasingdistortion, by thinning out (sub sampling) the image through a low passfilter according to a reduction rate, a part or the whole of the imagemay be reduced, or the image may maintain the size without passingthrough a filter.

Furthermore, when an image is projected in an inclined direction, inorder to prevent an image from being blurred due to out-of-focus on theperiphery portion, an edge enhancement process using an operator such asLaplacian or an edge enhancement process applying one-dimensionalfilters in horizontal and vertical directions may be performed. Throughthis edge enhancement process, the edge of a blurred image portion thatis projected can be enhanced.

In addition, in order to prevent the brightness of the whole screen frombeing changed due to a change in the projection size (area) according toa trapezoidal correction or the like that is performed by the keystonecorrection unit 108 to be described later, the image processing unit 102may perform adaptive luminance adjustment for the image data so as touniformly maintain the brightness. Furthermore, in a case where aperiphery portion of a projected image texture includes a diagonal line,in order not to allow an edge jag to be visually noticed, by mixing alocal halftone or applying a local low pass filter using the imageprocessing unit 102, the edge jag is shaded off, whereby the diagonalline can be prevented from being observed as a jagged line.

The image data output from the image processing unit 102 is supplied tothe keystone correction unit 108. The keystone correction unit 108performs a trapezoidal distortion correction (hereinafter, also simplyreferred to as a trapezoidal correction) for the supplied image data andsupplies the image data after the trapezoidal correction to the displayelement 114. Actually, this image data is supplied to the drive circuitthat drives the display element 114. The drive circuit drives thedisplay element 114 based on the supplied image data. The trapezoidalcorrection will be described later in detail.

The input control unit 119 receives a user operation input from theoperation unit 14 as an event.

The rotation control unit 104, for example, receives an instructionaccording to a user operation for the operation unit 14 through theinput control unit 119 and instructs the rotation mechanism unit 105based on the instruction according to the user operation. The rotationmechanism unit 105 includes the drive unit 32 and the photo interrupters51 a and 51 b described above. The rotation mechanism unit 105 controlsthe drive unit 32 according to an instruction supplied from the rotationcontrol unit 104, thereby controlling the rotation operation of the drumunit 10 (drum 30). For example, the rotation mechanism unit 105generates a drive pulse 122 according to an instruction supplied fromthe rotation control unit 104 and drives the motor 40 that is, forexample, a stepping motor.

Meanwhile, outputs of the photo interrupters 51 a and 51 b describedabove and the drive pulse 122 used for driving the motor 40 are suppliedfrom the rotation mechanism unit 105 to the rotation control unit 104.The rotation control unit 104, for example, includes a counter andcounts the pulse number of the drive pulses 122. The rotation controlunit 104 acquires the timing of detection of the protrusion 46 a basedon the output of the photo interrupter 51 b and resets the pulse numbercounted by the counter at the timing of the detection of the protrusion46 a. The rotation control unit 104, based on the pulse number countedby the counter, can sequentially acquire the angle of the drum unit 10(drum 30), thereby deriving the posture (in other words, the projectionangle of the projection lens 12) of the drum unit 10. In this way, in acase where the projection direction of the projection lens 12 ischanged, the rotation control unit 104 can derive an angle between aprojection direction before change and a projection angle after thechange. The derived projection angle 123 of the projection lens 12 issupplied to the image control unit 103.

The view angle control unit 106, for example, receives an instructionaccording to a user operation for the operation unit 14 through theinput control unit 119 and gives a zoom instruction, in other words, aninstruction for changing the view angle to the projection lens 12 basedon an instruction according to the user operation. The lens driving unitof the projection lens 12 drives the lens based on the zoom instruction,thereby performing zoom control. The view angle control unit 106supplies the zoom instruction and a view angle 125 derived based on azoom magnification relating to the zoom instruction and the like to theimage control unit 103.

The image control unit 103 designates an image cut out area using theimage cut-out unit 100 based on the projection angle 123 supplied fromthe rotation control unit 104 and the view angle 125 supplied from theview angle control unit 106. At this time, the image control unit 103designates a cut out area of the image data based on a line positionaccording to the angle between the projection directions before andafter the change of the projection lens 12.

The registration unit 118 receives the projection angle 123 at a timepoint when a predetermined key is pressed using the operation unit 14from the input control unit 119 and stores the received projection angle123 in the boundary storage unit 109. The boundary storage unit 109 is amemory medium such as a memory or a hard disk drive device (HDD).

The keystone adjustment unit 107 calculates and adjusts correctioncoefficients (to be described later) used for a trapezoidal correctionbased on the projection angle 123 input from the rotation control unit104 and the view angle 125 input from the view angle control unit 106.The keystone correction unit 108 performs a trapezoidal correction ofwhich the correction amount is adjusted based on the calculatedcorrection coefficients for the image data output from the imageprocessing unit 102.

The registration unit 118, the boundary storage unit 109, the keystoneadjustment unit 107, and the keystone correction unit 108 will bedescribed later in detail.

Cutting Out Process of Image Data

Next, a cutting out process of image data stored in the memory 101 thatis performed by the image control unit 103 and the image cut-out unit100 according to this embodiment will be described. FIG. 5 is aconceptual diagram that illustrates the cutting out process of imagedata stored in the memory 101 according to the first embodiment. Anexample of cutting out a image data 141 of a designated cut out areafrom a image data 140 stored in the memory 101 will be described withreference to a left diagram in FIG. 5.

In the memory 101, for example, addresses are set in the verticaldirection in units of lines and are set in the horizontal direction inunits of pixels. In addition, it is assumed that the address of a lineincreases from the lower end of an image (screen) toward the upper endthereof, and the address of a pixel increases from the left end of theimage toward the right end thereof.

The image control unit 103, for the image cut-out unit 100, designatesaddresses of lines q₀ and q₁ in the vertical direction and designatesaddresses of pixels p₀ and p₁ in the horizontal direction as a cut outarea of the image data 140 of Q lines×P pixels stored in the memory 101.The image cut-out unit 100 reads lines within the range of the lines q₀and q₁ over the pixels p₀ and p₁ from the memory 101 in accordance withthe designation of the addresses. At this time, as the sequence ofreading, for example, it is assumed that the lines are read from theupper end toward the lower end of the image, and the pixels are readfrom the left end toward the right end of the image. The access controlfor the memory 101 will be described in detail later.

The image cut-out unit 100 supplies the image data 141 of the range ofthe lines q₀ and q₁ and the pixels p₀ and p₁, which has been read fromthe memory 101, to the image processing unit 102. The image processingunit 102 performs a size conversion process in which the size of animage according to the supplied image data 141 is adjusted to the sizeof the display element 114. As an example, in a case where the size ofthe display element 114 is V lines×H pixels, a maximum multiplication msatisfying both Equations (1) and (2) as represented below is acquired.Then, the image processing unit 102 enlarges the image data 141 withthis multiplication m and, as illustrated in a diagram illustrated onthe right side in FIG. 5 as an example, size-converted image data 141′is acquired.m×(p ₁ −p ₀)≦H  (1)m×(q ₁ −q ₀)≦V  (2)

Next, the designation (update) of a cut out area according to theprojection angle according to this embodiment will be described. FIG. 6illustrates an example of designation of a cut out area of a case wherethe drum unit 10 is at the 0° posture, in other words, in a case wherethe projection angle is 0°.

In FIG. 5 described above, a case has been described as an example inwhich the image data 141 of the range of the pixels p₀ and p₁ that is apartial range of pixels of one line of the image data 140 of Q lines×Ppixels stored in the memory 101 is cut out. Also in examples illustratedin FIGS. 6 to 8, actually, pixels of a partial range of one line of theimage data 140 stored in the memory 101 may be cut out. However, inorder to simplify the description of the designation (update) of a cutout area according to the projection angle, in the examples representedin FIGS. 6 to 8 illustrated below, all the pixels of one line areassumed to be cut out.

In the projector device (PJ) 1, a projection position of a case where animage 131 ₀ is projected with a projection angle of 0° onto a projectionface 130 that is a projection medium such as a screen by using aprojection lens 12 having a view angle α is assumed to be a positionPos₀ corresponding to the luminous flux center of light projected fromthe projection lens 12. In addition, at the projection angle of 0°, animage according to image data from the S-th line that is the lower endof an area designated in advance to the L-th line is assumed to beprojected such that the image data stored in the memory 101 is projectedat the posture of a projection angle of 0°. In the area formed by linesof the S-th line to the L-th line, lines corresponding to the linenumber ln are included. In addition, a value representing a lineposition such as the S-th line or the L-th line, for example, is a valueincreasing from the lower end toward the upper end of the displayelement 114 with the line positioned at the lower end of the displayelement 114 set as the 0-th line.

Here, the line number ln is the number of lines of a maximal effectivearea of the display element 114. In addition, the view angle α is anangle for viewing a projection image in the vertical direction from theprojection lens 12 in a case where the image is projected when aneffective area in the vertical direction, in which the display iseffective in the display element 114, has a maximum value, in otherwords, in a case where an image of the line number ln is projected.

The view angle α and the effective area of the display element 114 willbe described using a more specific example. The display element 114 isassumed to have a vertical size of 800 lines. For example, in a casewhere the vertical size of the projection image data is 800 lines, andprojection image data is projected using all the lines of the displayelement 114, the effective area of the display element 114 in thevertical direction has a maximum value of 800 lines (=line number ln).In this case, the view angle α is an angle for viewing 1st to 800thlines of the projection image from the projection lens 12.

In addition, a case may be also considered in which the vertical size ofprojection image data is 600 lines, and the projection image data isprojected using only 600 lines out of 800 lines (=line number ln) of thedisplay element 114. In such a case, the effective area of the displayelement 114 in the vertical direction is 600 lines. In this case, only aportion of the effective area according to the projection image datawith respect to a maximal value of the effective area of the view angleα is projected.

The image control unit 103 instructs the image cut-out unit 100 to cutout and read the S-th line to L-th line of the image data 140 stored inthe memory 101. Here, in the horizontal direction, all the image data140 of the left end to the right end is read. The image cut-out unit 100sets an area of the S-th line to the L-th line of the image data 140 asa cut out area in accordance with an instruction from the image controlunit 103, reads the image data 141 of the set cut out area, and suppliesthe read image data to the image processing unit 102. In the exampleillustrated in FIG. 6, onto the projection face 130, an image 131 ₀according to image data 141 ₀ of the line number ln from the S-th lineto the L-th line of the image data 140 is projected. In such a case, animage according to image data 142 of an area relating to the L-th lineto the upper-end line out of the whole area of the image data 140 is notprojected.

Next, a case will be described in which the drum unit 10 is rotated, forexample, according to a user operation for the operation unit 14, andthe projection angle of the projection lens 12 becomes an angle θ. Inthis embodiment, in a case where the drum unit 10 is rotated, and theprojection angle according to the projection lens 12 is changed, the cutout area from the memory 101 of the image data 140 is changed inaccordance with the projection angle θ.

The setting of a cut out area for the projection angle θ will bedescribed more specifically with reference to FIG. 7. For example, acase will be considered in which the drum unit 10 is rotated in theforward direction from a projection position of the 0° posture accordingto the projection lens 12, and the projection angle of the projectionlens 12 becomes an angle θ (>0°). In such a case, the projectionposition for the projection face 130 moves to a projection position Pos₁that is located on the upper side of a projection position Pos₀corresponding to a projection angle of 0°. At this time, the imagecontrol unit 103, for the image cut-out unit 100, designates a cut outarea for the image data 140 stored in the memory 101 based on thefollowing Equations (3) and (4). Equation (3) represents an R_(S)-thline located at the lower end of the cut out area, and Equation (4)represents an R_(L)-th line located at the upper end of the cut outarea.R _(S)=θ×(ln/α)+S  (3)R _(L)=θ×(ln/α)+S+ln  (4)

In Equations (3) and (4), a value ln represents the number of lines (forexample, the number of lines of the display element 114) included withinthe projection area. In addition, a value α represents a view angle ofthe projection lens 12, and a value S represents a position of a linelocated at the lower end of the cut out area at the 0° posture describedwith reference to FIG. 6.

In Equations (3) and (4), (ln/α) represents the number of lines(including a concept of an approximately averaged number of lineschanging in accordance with the shape of the projection face) per unitangle of a case where the view angle α projects the line number ln.Accordingly, θ×(ln/α) represents the number of lines corresponding tothe projection angle θ according to the projection lens 12 in theprojector device 1. This means that, when the projection angle changesby an angle Δθ, the position of the projection image is moved by adistance corresponding to the number of lines {Δθ×(ln/α)} in theprojection image. Accordingly, Equations (3) and (4) respectivelyrepresent the positions of lines located at the lower end and the upperend of the image data 140 in the projection image of a case where theprojection angle is the angle θ. This corresponds to a read address forthe image data 140 on the memory 101 at the projection angle θ.

In this way, in this embodiment, an address at the time of reading theimage data 140 from the memory 101 is designated in accordance with theprojection angle θ. Accordingly, for example, in the example illustratedin FIG. 7, image data 141 ₁ of the image data 140 that is located at aposition corresponding to the projection angle θ is read from the memory101, and an image 131 ₁ relating to the read image data 141 ₁ isprojected to the projection position Pos₁ corresponding to theprojection angle θ of the projection face 130.

Thus, according to this embodiment, in a case where the image data 140having a size larger than the size of the display element 114 isprojected, a correspondence relation between the position within theprojected image and the position within the image data is maintained. Inaddition, since the projection angle θ is acquired based on a drivepulse of the motor 40 used for driving the drum 30 to be rotated, theprojection angle θ can be acquired in a state in which there issubstantially no delay with respect to the rotation of the drum unit 10,and the projection angle θ can be acquired without being influenced bythe projection image or the surrounding environment.

Next, the setting of a cut out area of a case where optical zoomingaccording to the projection lens 12 is performed will be described. Asdescribed above, in the case of the projector device 1, the view angle αof the projection lens 12 is increased or decreased by driving the lensdriving unit, whereby optical zooming is performed. An increase in theview angle according to the optical zooming is assumed to be an angle Δ,and the view angle of the projection lens 12 after the optical zoomingis assumed to be a view angle (α+Δ).

In such a case, even when the view angle is increased according to theoptical zooming, the cut out area for the memory 101 does not change. Inother words, the number of lines included in a projection imageaccording to the view angle α before the optical zooming and the numberof lines included in a projection image according to the view angle(α+Δ) after the optical zooming are the same. Accordingly, after theoptical zooming, the number of lines included per unit angle is changedfrom that before the optical zooming.

The setting of a cut out area of a case where optical zooming isperformed will be described more specifically with reference to FIG. 8.In the example illustrated in FIG. 8, optical zooming is performed inwhich the view angle α is increased by an amount corresponding to theview angle Δ in the state of the projection angle θ. By performing theoptical zooming, for example, a projection image projected onto theprojection face 130, as illustrated as an image 131 ₂, is enlarged by anamount corresponding to the view angle Δ with respect to that of a casewhere the optical zooming is not performed with the center (theprojection position Pos₂) of the luminous fluxes of light projected fromthe projection lens 12 in common.

In a case where optical zooming corresponding to the view angle Δ isperformed, when the number of lines designated as a cut out area for theimage data 140 is ln, the number of lines included per unit angle isrepresented by {ln/(α+Δ)}. Accordingly, the cut out area for the imagedata 140 is designated based on the following Equations (5) and (6). Themeaning of each variable in Equations (5) and (6) is common to that inEquations (3) and (4) described above.R _(S)=θ×{ln/(α+Δ)}+S  (5)R _(L)=θ×{ln/(α+Δ)}+S+ln  (6)

Image data 141 ₂ of an area represented in Equations (5) and (6) is readfrom the image data 140, and an image 131 ₂ relating to the read imagedata 141 ₂ is projected to a projection position Pos₂ of the projectionface 130 by the projection lens 12.

In this way, in a case where optical zooming is performed, the number oflines included per unit angle is changed with respect to a case wherethe optical zooming is not performed, and the amount of change in thenumber of lines with respect to a change in the projection angle θ isdifferent from that of a case where the optical zooming is notperformed. This is a state in which a gain corresponding to the viewangle Δ increased according to the optical zooming is changed in thedesignation of a read address according to the projection angle θ forthe memory 101.

In this embodiment, an address at the time of reading the image data 140from the memory 101 is designated in accordance with the projectionangle θ and the view angle α of the projection lens 12. In this way,even in a case where optical zooming is performed, the address of theimage data 141 ₂ to be projected can be appropriately designated for thememory 101. Accordingly, even in a case where the optical zooming isperformed, when the image data 140 of a size larger than the size of thedisplay element 114 is projected, a correspondence relation between theposition within the projected image and the position within the imagedata is maintained.

Next, a case will be described with reference to FIG. 9 in which anoffset is given to the projection position of the image. When theprojector device 1 is used, it cannot be determined that the 0° posture(projection angle 0°) is necessarily the lowest end of the projectionposition. For example, as illustrated in FIG. 9, a case may beconsidered in which a projection position Pos₃ according to apredetermined projection angle θ_(ofst) is set as the projectionposition located at the lowest end. In such a case, a image 131 ₃according to a image data 141 ₃ is projected to a position shifted tothe upper side by a height corresponding to the projection angleθ_(ofst) compared to a case where the offset is not given. Theprojection angle θ at the time of projecting an image having a linelocated at the lowest end of the image data 140 as its lowest end is setas the offset angle θ_(ofst) according to the offset.

In such a case, for example, a case may be considered in which theoffset angle θ_(ofst) is regarded as the projection angle 0°, and a cutout area for the image memory 101 is designated. By applying Equations(3) and (4) described above, the following Equations (7) and (8) areformed. The meaning of each variable in Equations (7) and (8) is commonto that in Equations (3) and (4) described above.R _(S)=(θ−θ_(ofst))×(ln/α)+S  (7)R _(L)=(θ−θ_(ofst))×(ln/α)+S+ln  (8)

The image data 141 ₃ of the area represented in Equations (7) and (8) isread from the image data 140, and the image 131 ₃ relating to the readimage data 141 ₃ is projected to the projection position Pos₃ of theprojection face 130 by the projection lens 12.

The method of designating a cut out area using Equations (3) and (4)described above is based on a cylindrical model in which the projectionface 130, for which projection is performed by the projection lens 12,is assumed to be a cylinder having the rotation shaft 36 of the drumunit 10 as its center. However, actually, the projection face 130 isfrequently considered to be a perpendicular face (hereinafter, simplyreferred to as a “perpendicular face”) forming an angle of 90° withrespect to the projection angle θ=0°. In a case where image data of thesame number of lines is cut out from the image data 140 and is projectedto the perpendicular face, as the projection angle θ increases, an imageprojected to the perpendicular face grows in the vertical direction.Thus, after the cut-out unit, image processing to be described next isperformed by the image processing unit.

The image projected to the perpendicular face will be described withreference to FIGS. 10 and 11. As illustrated in FIG. 10, a case will beconsidered in which an image is projected from the projection lens 12onto a projection face 204 that is disposed to be separate from aposition 201, which is the position of the rotation shaft 36 of the drumunit 10, by a distance r.

In the cylindrical model described above, a projection image isprojected with an arc 202 that has the position 201 as its center andhas a radius r being the projection face. Each point on the arc 202 hasthe same distance from the position 201, and the center of the luminousfluxes of light projected from the projection lens 12 is a radius of acircle including the arc 202. Accordingly, even when the projectionangle θ is increased from an angle θ₀ of 0° to an angle θ₁, an angle θ₂,. . . , the projection image is projected to the projection face withthe same size all the time.

On the other hand, in a case where an image is projected from theprojection lens 12 onto the projection face 204 that is a perpendicularface, when the projection angle θ is increased from an angle θ₀ to anangle θ₁, an angle θ₂, . . . , a position on the projection face 204 towhich the center of luminous fluxes of light emitted from the projectionlens 12 is projected changes according to the characteristics of atangent function as a function of the angle θ. Accordingly, theprojection image grows upwardly in accordance with a ratio M representedin the following Equation (9) as the projection angle θ increases.M=(180×tan θ)/(θ×π)  (9)

According to Equation (9) described above, for example, in the case ofthe projection angle θ=45°, the projection image grows at the ratio ofabout 1.27 times. In addition, in a case where the projection face W ismuch higher than the length of the radius r, and projection at theprojection angle θ=60° can be performed, in the case of the projectionangle θ=60°, the projection image grows at the ratio of about 1.65times.

In addition, as illustrated in FIG. 11 as an example, a line gap 205 inthe projection image on the projection face 204 is widened as theprojection angle θ increases. In this case, the line gap 205 is widenedbased on Equation (9) described above in accordance with the position onthe projection face 204 within one projection image.

Thus, the projector device 1, in accordance with the projection angle θof the projection lens 12, performs a reduction process for the imagedata of an image to be projected at the ratio of the reciprocal ofEquation (9) described above. In this reduction process, image data ispreferably larger than the image data cut out based on the cylindermodel. In other words, while the image data depends on the height of theprojection face 204 that is a perpendicular face, in the case of theprojection angle θ=45°, the projected image grows at the ratio of about1.27 times, and accordingly, the image data is reduced at the ratio ofthe reciprocal thereof that is about 78%.

For example, when image data input to the projector device 1 is storedin the memory 101 by the image cut-out unit 100, the image control unit103 performs a reduction process for the image data in advance for eachline of an image at the time of projecting the image data by using aratio of the reciprocal of Equation (9) described above. In thereduction process, a low pass filter process is performed for lines(pixels in the vertical direction) at a reduction rate depending on theprojection angle θ by using a low pass filter having several taps,whereby the line is thinned out. More precisely, in the low pass filterprocess, it is preferable that the limit value of the band of the lowpass filter is also changed depending on the projection angle θ.However, the low pass filter process is not limited thereto, but ageneral linear interpolation for uniformly determining thecharacteristics of the filter at a reduction rate corresponding to amaximal projection angle θ or a general linear interpolation foruniformly determining the characteristics of the filter at a reductionrate corresponding to an about half of the maximum projection angle θmay be used. In addition, after the filter process, it is preferable toperform sub sampling of the line to be thinned out depending on theprojection angle θ within the screen.

However, the process is not limited thereto, but a process for uniformlythinning-out at a reduction rate corresponding to a maximum projectionangle θ, a process for uniformly thinning out at a reduction ratecorresponding to an almost half of the maximum projection angle θ, orthe like may be performed. In a case where the low pass filter processand the thinning-out process are to be performed more precisely, bydividing image data into several areas in the line direction anduniformly applying the processes for each divided area, further improvedcharacteristics can be acquired.

In addition, in this embodiment, the image processing using Equation (9)is not limited to be performed by the image cut-out unit 100 when theimage data is stored in the memory 101. For example, the imageprocessing using Equation (9) may be configured to be performed by theimage processing unit 102.

Furthermore, in an environment in which the projector device 1 isactually used, there is a limitation on the height of the projectionface 204, and it is considered that there are many cases where a face203 is formed by being turned by 90° at a position 200 of a certainheight. This face 203 may be used as a projection face of the projectordevice 1 as well. In such a case, as the projection angle θ of an imageprojected onto the projection face 203 is further increased, and, theprojection position passes the position 200 and is directed toward theright upward direction (the projection angle θ=90°, the projected imageis reduced according to a characteristic that is opposite to that of theimage projected onto the projection face 204 described above.

Accordingly, in a case where an image according to the image data isprojected with a projection angle of 0° or 90°, the reduction processusing Equation (9) is not performed for the image data to be projected.In addition, in a case where the length (height) of the projection face204 and the length of the projection face 203 are approximately thesame, the reduction process using Equation (9) for the image data to beprojected is performed by a reduction process from a projection angle of0° to the position 200 of the uppermost portion of the projection face Wand a reduction process from the position 200 to a projection angle of90° as processes symmetrical to each other. Accordingly, the load of theimage control unit 103 for the reduction process can be reduced.

In the example described above, the perpendicular face forming an angleof 90° with respect to the projection angle θ=0° has been considered forthe description. Depending on the rotation angle of the drum unit 10, acase may be considered in which image data is projected onto a planeforming an angle of 180° with respect to the projection angle θ=0°. In acase where image data corresponding to the same number of lines is cutout from the image data 140 and is projected to the face, as theprojection angle θ increases, the projected image is reduced in thevertical direction. Thus, after the image cut-out unit 100, the imageprocessing unit 102 performs image processing that is opposite to thatdescribed above.

In other words, when the projection angle θ is increased from an angleθ₀ to an angle θ₁, an angle θ₂, . . . , a distance from the projectionunit to the projection face changes to be decreased. Thus, the projectordevice 1, in accordance with the projection angle θ of the projectionlens 12, opposite to the description presented above, performs anenlargement process of the image data of an image to be projected.

As described above, in a case where a distance from the projection lens12 to the projection face decreases according to a change in theprojection direction from the first projection direction to the secondprojection direction, the image cut-out unit of the projector device 1may be configured to perform an enlargement process based on theprojection angle θ for each pixel of the cut out image data.

Hereinafter, unless otherwise described, the description of the angle isassumed to be based on the cylinder model, and, as is necessary as inthe case of projection for the perpendicular face or the like, acorrection that is based on Equation (9) is performed as is appropriate.

Memory Control

Next, access control of the memory 101 will be described with referenceto FIGS. 12 to 15. In the image data, for each vertical synchronizationsignal 124, pixels are sequentially transmitted from the left end towardthe right end of an image for each line in the horizontal direction on ascreen, and lines are sequentially transmitted from upper end toward thelower end of the image. Hereinafter, a case will be described as anexample in which the image data has a size of horizontal 1920pixels×vertical 1080 pixels (lines) corresponding to the digital highvision standard. In addition, hereinafter, unless otherwise described,the vertical synchronization signal 124 will be described as a verticalsynchronization signal VD.

Hereinafter, an example of the access control of a case where the memory101 includes four memory areas for which the access control can beindependently performed will be described. In other words, asillustrated in FIG. 12, in the memory 101, areas of memories 101Y₁ and101Y₂ used for writing and reading image data with a size of horizontal1920 pixels and vertical 1080 pixels (lines) and areas of memories 101T₁and 101T₂ used for writing and reading image data with a size ofhorizontal 1080 pixels×vertical 1920 pixels (lines) are arranged.Hereinafter, the memories 101Y₁, 101Y₂, 101T₁, and 101T₂ will bedescribed as memories Y₁, Y₂, T₁, and T₂.

FIG. 13 is a timing diagram that illustrates access control of thememory 101 using the image cut-out unit 100 according to the firstembodiment. In FIG. 13, Chart 210 represents the projection angle θ ofthe projection lens 12, and Chart 211 represents the verticalsynchronization signal VD. In addition, Chart 212 represents inputtimings of image data D₁, D₂, and . . . input to the image cut-out unit100, and Charts 213 to 216 represent examples of accesses to thememories Y₁, Y₂, T₁, and T₂ from the image cut-out unit 100. Inaddition, in Charts 213 to 216, each block to which “R” is attachedrepresents reading, and each block to which “W” is attached representswriting.

For every vertical synchronization signal VD, image data D₁, D₂, D₃, D₄,D₅, D₆, . . . each having an image size of 1920 pixels×1080 lines areinput to the image cut-out unit 100. Each of the image data D₁, D₂, . .. is synchronized with the vertical synchronization signal VD and isinput after the vertical synchronization signal VD. In addition, theprojection angles of the projection lens 12 corresponding to thevertical synchronization signals VD are denoted as projection angles θ₁,θ₂, θ₃, θ₄, θ₅, θ₆, . . . . The projection angle θ is acquired for everyvertical synchronization signal VD as described above.

First, the image data D₁ is input to the image cut-out unit 100. Asdescribed above, the projector device 1 according to this embodimentchanges the projection angle θ according to the projection lens 12 byrotating the drum unit 10 so as to move the projection position of theprojection image and designates a read position for the image data inaccordance with the projection angle θ. Accordingly, it is preferablethat the image data is longer in the vertical direction. Generally,image data frequently has a horizontal size longer than a vertical size.Thus, for example, it may be considered for a user to rotate the cameraby 90° in an imaging process and input image data acquired by theimaging process to the projector device 1.

In other words, an image according to the image data D₁, D₂, . . . inputto the image cut-out unit 100, similarly to an image 160 illustrated asan image in FIG. 14A, is an image facing the side acquired by rotating aright-direction image by 90° that is determined based on the content ofthe image.

The image cut-out unit 100 first writes the input image data D₁ into thememory Y₁ at timing WD₁ corresponding to the input timing of the imagedata D₁ (timing WD₁ represented in Chart 213). The image cut-out unit100 writes the image data D₁ into the memory Y₁, as illustrated on theleft side of FIG. 14B, in the sequence of lines toward the horizontaldirection. On the right side of FIG. 14B, an image 161 according to theimage data D₁ written into the memory Y₁ as such is illustrated as animage. The image data D₁ is written into the memory Y₁ as the image 161that is the same as the input image 160.

The image cut-out unit 100, as illustrated in FIG. 14C, reads the imagedata D₁ written into the memory Y₁ from the memory Y₁ at timing RD₁ thatis the same as the timing of start of a next vertical synchronizationsignal VD after the vertical synchronization signal VD for writing theimage data D₁ (timing RD₁ represented in Chart 213).

At this time, the image cut-out unit 100 sequentially reads the imagedata D₁ in the vertical direction over the lines for each pixel with apixel positioned on the lower left corner of the image being set as areading start pixel. When pixels positioned at the upper end of theimage are read, next, pixels are read in the vertical direction with apixel positioned on the right side neighboring to the pixel positionedat the reading start position of the vertical direction being set as areading start pixel. This operation is repeated until the reading of apixel positioned on the upper right corner of the image is completed.

In other words, the image cut-out unit 100 sequentially reads the imagedata D₁ from the memory Y₁ for each line in the vertical direction fromthe left end toward the right end of the image for each pixel with theline direction being set as the vertical direction from the lower endtoward the upper end of the image.

The image cut-out unit 100 sequentially writes the pixels of the imagedata D₁ read from the memory Y₁ in this way, as illustrated on the leftside in FIG. 15A, into the memory T₁ toward the line direction for eachpixel (timing WD₁ represented in Chart 214). In other words, forexample, every time when one pixel is read from the memory Y₁, the imagecut-out unit 100 writes one pixel that has been read into the memory T₁.

On the right side in FIG. 15A, an image 162 according to the image dataD₁ written into the memory T₁ in this way is illustrated. The image dataD₁ is written into the memory T₁ with a size of horizontal 1080pixels×vertical 1920 pixels (lines) and is the image 162 acquired byrotating the input image 160 by 90° in the clockwise direction andinterchanging the horizontal direction and the vertical direction.

The image cut-out unit 100 designates an address of the cut out areathat is designated by the image control unit 103 to the memory T₁ andreads image data of the area designated as the cut out area from thememory T₁. The timing of this reading process, as represented by timingRD₁ in Chart 214, is delayed from the timing at which the image data D₁is input to the image cut-out unit 100 by two vertical synchronizationsignals VD.

The projector device 1 according to this embodiment, as described above,moves the projection position of the projection image by rotating thedrum unit 10 so as to change the projection angle θ according to theprojection lens 12 and designates a reading position for image data inaccordance with the projection angle θ. For example, the image data D₁is input to the image cut-out unit 100 at the timing of the projectionangle θ₁. The projection angle θ at the timing when an image accordingto the image data D₁ is actually projected may be changed from theprojection angle θ₁ to a projection angle θ₃ different from theprojection angle θ₁.

Accordingly, the cut out area at the time of reading the image data D₁from the memory T₁ is read from a range that is larger than the area ofimage data corresponding to the projected image in consideration of achange in the projection angle θ.

The description will be described more specifically with reference toFIG. 15B. The left side in FIG. 15B illustrates an image 163 accordingto the image data D₁ stored in the memory T₁. In this image 163, an areathat is actually projected is represented as a projection area 163 a,and the other area 163 b is represented as a non-projection area. Inthis case, the image control unit 103 designates a cut out area 170 thatis larger than the area of the image data corresponding to the image ofthe projection area 163 by at least the number of lines corresponding toa change of a case where the projection angle θ according to theprojection lens 12 maximally changes during a period of two verticalsynchronization signals VD for the memory T₁ (see the right side in FIG.15B).

The image cut-out unit 100 reads the image data from this cut out area170 at the timing of a next vertical synchronization signal VD after thevertical synchronization signal VD for writing the image data D₁ intothe memory T₁. In this way, at the timing of the projection angle θ₃,the image data to be projected is read from the memory T₁, is suppliedto the display element 114 through the image processing unit 102 of alater stage, and is projected from the projection lens 12.

At the timing of the next vertical synchronization signal VD after thevertical synchronization signal VD for which the image data D₁ is input,the image data D₂ is input to the image cut-out unit 100. At thistiming, the image data D₁ is written into the memory Y₁. Accordingly,the image cut-out unit 100 writes the image data D₂ into the memory Y₂(timing WD₂ represented in Chart 215). The sequence of writing the imagedata D₂ into the memory Y₂ at this time is similar to the sequence ofwriting the image data D₁ described above into the memory Y₁, and thesequence for the image is similar to that described above (see FIG.14B).

In other words, the image cut-out unit 100 sequentially reads the imagedata D₂ in the vertical direction over the lines for each pixel up tothe pixel positioned at the upper end of the image with a pixelpositioned on the lower left corner of the image being set as a readingstart pixel, and next, pixels are read in the vertical direction with apixel positioned on the right side neighboring to the pixel positionedat the reading start position of the vertical direction being set as areading start pixel (timing RD₂ represented in Chart 215). Thisoperation is repeated until the reading of a pixel positioned on theupper right corner of the image is completed. The image cut-out unit 100sequentially writes (timing WD₂ represented in Chart 216) the pixel ofthe image data D₂ read from the memory Y₂ in this way into the memory T₂toward the line direction for each pixel (see the left side in FIG.15A).

The image cut-out unit 100 designates an address of the cut out areathat is designated by the image control unit 103 to the memory T₂ andreads image data of the area designated as the cut out area from thememory T₂ at timing RD₂ represented in Chart 216. At this time, asdescribed above, the image control unit 103 designates an area lagerthan the area of the image data corresponding to the projected image asthe cut out area 170 in consideration of a change in the projectionangle θ for the memory T₂ (see the right side in FIG. 15B).

The image cut-out unit 100 reads the image data from this cut out area170 at the timing of a next vertical synchronization signal VD after thevertical synchronization signal VD for writing the image data D₂ intothe memory T₂. In this way, the image data of the cut out area 170 ofthe image data D₂ input to the image cut-out unit 100 at the timing ofthe projection angle θ₂ is read from the memory T₂ at the timing of theprojection angle θ₄, is supplied to the display element 114 through theimage processing unit 102 of a later stage, and is projected from theprojection lens 12.

Thereafter, similarly, for the image data D₃, D₄, D₅, . . . , theprocess is sequentially performed using a set of the memories Y₁ and T₁and a set of the memories Y₂ and T₂ in an alternate manner.

As described above, according to this embodiment, in the memory 101, anarea of the memories Y₁ and Y₂ used for writing and reading image datawith the size of horizontal 1920 pixels×vertical 1080 pixels (lines) andan area of the memories T₁ and T₂ used for writing and reading imagedata with the size of horizontal 1080 pixels×vertical 1920 pixels(lines) are arranged. The reason for this is that, generally, a DRAM(Dynamic Random Access Memory) used for an image memory has an accessspeed for the vertical direction that is lower than an access speed forthe horizontal direction. In a case where another memory, which iseasily randomly accessible, having access speeds of the same level forthe horizontal direction and the vertical direction is used, aconfiguration may be employed in which a memory having a capacitycorresponding to the image data is used in both the cases.

Trapezoidal Correction

Next, the calculation of correction coefficients used for a trapezoidalcorrection performed by the keystone adjustment unit 107 and thetrapezoidal correction performed by the keystone correction unit 108based on the calculated correction coefficients will be described.First, a conventional trapezoidal correction will be described. FIGS.31A and 31B are diagrams that illustrate a case where the trapezoidalcorrection is not performed.

FIG. 31A illustrates a conventional projector device 3100 and projectionangles θ and projection directions of a case where a floor face 3101, awall face 3102, and a ceiling 3103 are set as projection faces. FIG. 31Billustrates shapes of projection images that are projected to and aredisplayed on projection faces of the wall face 3102 and the ceiling 3103for each projection direction illustrated in FIG. 31A. In FIG. 31B, ashape 3120 is a shape of a projection image displayed on the projectionface in a projection direction 3110, a shape 3121 is a shape of aprojection image displayed on the projection face in a projectiondirection 3111, a shape 3122 is a shape of a projection image displayedon the projection face in a projection direction 3112, a shape 3123 is ashape of a projection image displayed on the projection face in aprojection direction 3113, and a shape 3124 is a shape of a projectionimage displayed on the projection face in a projection direction 3114.

Here, the projection direction 3110 is a projection direction of a casewhere an angle formed by the optical axis of the projection lens of theprojector device 3100 and the wall face 3102 is a right angle, in otherwords, in a case where the projection direction is a horizontaldirection. In such a case, generally, the projection image projected tothe wall face 3102, as illustrated in the shape 3120, is designed to bea rectangular shape.

For the purpose of projection for the upper side of the wall face 3102,when the projection angle θ is increased by upwardly inclining theprojection lens of the projector device 3100 such that the projectiondirection 3111 is set, in a case where a so-called trapezoidalcorrection is not performed, the shape of a projection image formed onthe wall face 3102, as illustrated in the shape 3121, is a trapezoid inwhich the upper side is longer than the lower side due to a differencein the projection distances.

In a case where the projection direction of the projection lens is setto the direction 3112 of the boundary between the wall face 3102 and theceiling 3103 by further increasing the projection angle θ, asillustrated in the shape 3122, the projection image is projected to boththe wall face 3102 and the ceiling 3103. In other words, a projectionimage having a shape 3122 is projected which has a trapezoidal portionhaving the upper side longer than the lower side on the wall face 3102and a trapezoidal portion having the upper side shorter than the lowerside at the ceiling 3103 with the boundary (represented by a boundary3112 b in the shape 3122 illustrated in FIG. 31B) between the wall face3102 and the ceiling 3103 formed as the boundary.

In a case where the projection direction of the projection lens is setto the projection direction 3113 toward the ceiling 3103 by furtherincreasing the projection angle θ, the projection image, as illustratedin the shape 3123, is a trapezoid of which the relative lengths betweenthe length of the upper side and the length of the lower side isreversed from those of the shape 3121 of the projection image on thewall face 3102 is formed.

Then, in a case where the angle formed by the optical axis of theprojection lens of the projector device 3100 and the ceiling 3103 is aright angle, in other words, in a case where the projection direction isa vertical direction (denoted as the projection direction 3114 in FIG.31A), the projection image projected to the ceiling, as illustrated inthe shape 3124, is a rectangle. As above, in the conventional projectordevice, the shape of a projection image that is projected to and isdisplayed on the projection face is distorted to a shape such as atrapezoid due to a difference between projection distances except forthe case of the projection directions 3110 and 3114.

For this reason, in the conventional projector device 3100, atrapezoidal correction, as described below, may be further performed forthe image data and the image data after the trapezoidal correction maybe projected. FIG. 32A illustrates the shape of an image relating toimage data after the trapezoidal correction, and FIG. 32B illustratesthe shape of a projection image acquired by projecting the image dataafter the trapezoidal correction illustrated in FIG. 32A to theprojection face.

A shape 3130 illustrated in FIG. 32A is the shape of an image relatingto the image data after the trapezoidal correction at the time of theprojection direction 3110 illustrated in FIG. 31A. A shape 3131illustrated in FIG. 32A is the shape of an image relating to the imagedata after the trapezoidal correction at the time of the projectiondirection 3111 illustrated in FIG. 31A. A shape 3132 illustrated in FIG.32A is the shape of an image relating to the image data after thetrapezoidal correction at a time when the projection direction is in arange between the projection direction 3111 and the projection direction3112 illustrated in FIG. 31A. A shape 3133 illustrated in FIG. 32A isthe shape of an image relating to the image data after the trapezoidalcorrection at a time when the projection direction is in a range betweenthe projection direction 3112 and the projection direction 3113illustrated in FIG. 31A. A shape 3134 illustrated in FIG. 32A is theshape of an image relating to the image data after the trapezoidalcorrection at the time of the projection direction 3113 illustrated inFIG. 31A. In addition, a shape 3135 illustrated in FIG. 32A is the shapeof an image relating to the image data after the trapezoidal correctionat the time of the projection direction 3114 illustrated in FIG. 31A.

A shape 3140 illustrated in FIG. 32B is the shape of a projection imagethat is projected to the wall face 3102 so as to be displayed thereonafter the trapezoidal correction at the time of the projection direction3110 illustrated in FIG. 31A. A shape 3141 illustrated in FIG. 32B isthe shape of a projection image that is projected to the wall face 3102so as to be displayed thereon after the trapezoidal correction at thetime of the projection direction 3111 illustrated in FIG. 31A. A shape3142 illustrated in FIG. 32B is the shape of a projection image that isprojected to the wall face 3102 and the ceiling 3103 so as to bedisplayed thereon after the trapezoidal correction at the time when theprojection direction is in a range between the projection direction 3111and the projection direction 3112 illustrated in FIG. 31A. A shape 3143illustrated in FIG. 32B is the shape of a projection image that isprojected to the wall face 3102 and the ceiling 3103 so as to bedisplayed thereon after the trapezoidal correction at the time when theprojection direction is in a range between the projection direction 3112and the projection direction 3113 illustrated in FIG. 31A. A shape 3144illustrated in FIG. 32B is the shape of a projection image that isprojected to the ceiling so as to be displayed thereon after thetrapezoidal correction at the time of the projection direction 3113illustrated in FIG. 31A. In addition, a shape 3145 illustrated in FIG.32B is the shape of a projection image that is projected to the ceiling3103 so as to be displayed thereon after the trapezoidal correction atthe time of the projection direction 3114 illustrated in FIG. 31A.

In a case where the projection direction is the projection direction3110, the projector device 3100 projects the shape 3130 of an imagerelating to image data to be projected to the wall face 3102 to the wallface with the shape not being changed to a trapezoidal shape but beingmaintained as a rectangular shape, in other words, with the correctionamount of the trapezoidal correction being set to zero. Then, on thewall face 3102, the projection image is displayed in the shape 3140 ofthe rectangle.

In a case where the projection direction is the projection direction3111, the projector device 3100 performs a correction shaping the shapeof an image relating to image data to be projected to the wall face 3102into the shape 3131 of an image that has a trapezoidal shape having therelation between the length of the upper side and the length of thelower side that is opposite to that of the trapezoidal shape of theshape 3121 illustrated in FIG. 31B and projects the image of the shape3131 after the correction to the wall face. As a result of thetrapezoidal correction, on the wall face, the projection image 3141having no trapezoidal distortion is displayed.

Similarly, in a case where the projection direction is the projectiondirection 3113, the conventional projector device 3100 performs acorrection shaping the shape of an image relating to image data to beprojected to the ceiling 3103 into the shape 3134 that has a trapezoidalshape having the relation between the length of the upper side and thelength of the lower side that is opposite to that of the trapezoidalshape of the shape 3123 illustrated in FIG. 31B and projects the imagedata of the shape 3134 after the correction to the ceiling 3103. As aresult, on the ceiling 3103, the projection image having the shape 3144having no trapezoidal distortion is displayed.

In a case where the projection direction is the projection direction3114, the projector device 3100 projects the shape 3135 of an imagerelating to image data to be projected to the ceiling 3103 to theceiling 3103 with the shape not being changed to a trapezoidal shape butbeing maintained as a rectangular shape, in other words, with thecorrection amount of the trapezoidal correction being set to zero. Then,on the ceiling 3103, the projection image having the shape 3145 of therectangle is displayed.

Here, in the conventional projector device 3100, when the projectiondirection becomes a predetermined direction set based on the boundarybetween the wall face 3102 and the ceiling 3103, in other words, in acase where the projection angle θ becomes a predetermined displacementangle set in advance, by reversing the left side and the right side ofthe trapezoid for the shape of the image relating to the image data tobe projected to the projection face, an appropriate trapezoidalcorrection is performed for the wall face 3102 and the ceiling 3103. Inthe example described above, for the projection direction 3112 and theprojection direction 3113, the upper side and the lower side of thetrapezoid are reversed between the shape 3131 of the image and the shape3134 of the image.

However, when the operation performed at the boundary between the wallface 3102 and the ceiling 3103 and near the boundary is reviewed indetail, there are inconveniences as below. In other words, in a casewhere the predetermined direction described above is set to theprojection direction 3112 or near the projection direction 3112, betweenbefore and after the projection direction becomes the predetermineddirection, the shape of an image relating to the image data is switchedfrom the shape 3132 to the shape 3133 illustrated in FIG. 32A, and theshape of a projection image displayed on the projection medium isswitched from the shape 3142 to the shape 3143 illustrated in FIG. 32B.Accordingly, between before and after the projection direction becomesthe predetermined direction, the shape of a projection image displayedon the projection medium is changed discontinuously.

In other words, for the shape 3132 of an image relating to the imagedata, the image is projected in the shape 3142 in which a portionprojected onto the wall face 3102 is a rectangle, and a portionprojected to the ceiling 3103 having the boundary as a border is atrapezoid. In addition, for the shape 3133 of an image relating to theimage data, the image is projected in the shape 3143 in which a portionprojected to the wall face 3102 is a trapezoid, and a portion projectedto the ceiling 3103 having the boundary as a border is rectangle. Theshape of the projection image is discontinuously changed to these shapes3142 and 3143 different from each other.

In addition, by moving the projection lens of the projector device 3100,in a case where the projection image is caused to reciprocate near theboundary between the wall face 3102 and the ceiling 3103 or in a casewhere the movement of the projection image is stopped at the boundarylimit, the switching between a positive/negative trapezoidal correctionis repeatedly performed, and an unstable video is formed, whereby it isdifficult to project a smooth and stable projection image that can beeasily viewed.

For this reason, in the projector device 1 according to this firstembodiment, by performing a trapezoidal correction of which thecorrection amount is adjusted in accordance with the projection angle θas below, the projection of a smooth and stable projection image thatcan be easily viewed is realized.

FIG. 16 is a diagram that illustrates the projector device 1 accordingto the first embodiment and major projection directions of theprojection lens 12 in a case where a floor face, a wall face, and aceiling are used as projection faces. Here, a projection direction 230illustrates a case where the optical axis of the projection lens 12 ofthe projector device 1 and a wall face 220 form a right angle, in otherwords, the horizontal direction, and a projection angle at this time isdefined as 0°.

A projection direction 231 is a direction of the boundary between thewall face 220 and a ceiling 221 that are two projection faces lined upto have a predetermined angle therebetween. In the example illustratedin FIG. 16, the predetermined angle is 90°. A projection direction 232is the projection direction of the projection lens 12 of a case where,in a rectangular projection image that is projected to the wall face 220so as to be projected thereon, the upper side corresponding to a firstside out of one pair of sides in a direction perpendicular to thevertical direction that is the movement direction of the projectionimage almost coincides with the boundary between the wall face 220 andthe ceiling 221.

A projection direction 233 is the projection direction of the projectionlens 12 of a case where the lower side corresponding to a second sideout of the one pair of sides of the projection image of the ceiling 221almost coincides with the boundary between the wall face 220 and theceiling 221. A projection direction 234 is the direction of the ceiling221 disposed right above the projector device 1 and is in a state inwhich the optical axis of the projection lens 12 and the ceiling 221form a right angle. The projection angle at this time is 90°.

The boundary storage unit 109 illustrated in FIG. 4 stores theprojection angle at the time of the projection direction 232 as a firstboundary start angle, stores the projection angle at the time of theprojection direction 231 as a first boundary angle, and stores theprojection angle at the time of the projection direction 233 as a firstboundary end angle.

In this embodiment, before projecting an image relating to a desiredcontent by starting the projector device 1, while a user, in a state inwhich a desired zoom magnification at the time of projecting the imagerelating to the desired content is set, projects an image relating toarbitrary image data, the user rotates the projection direction of theprojection lens 12 from a floor face 222 to the wall face 220 and theceiling 221.

Then, every time when the upper side corresponding to the first side outof one pair of sides disposed in a direction perpendicular to thevertical direction that is the movement direction of a projection imagearrives at the projection direction 232 that almost coincides with theboundary between the wall face 220 and the ceiling 221, or the lowerside corresponding to the second side out of one pair of sides of theprojection image arrives at the projection direction 233 that almostcoincides with the boundary between the wall face 220 and the ceiling221 or arrives at the projection direction 231 in which the optical axisalmost coincides with the boundary, when the registration unit 118receives events of key pressing in accordance with the pressing of apredetermined key using the operation unit 14, projection angles at timepoints when the key is pressed are registered in the boundary storageunit 109 as a first boundary start angle, a first boundary angle, and afirst boundary end angle.

Hereinafter, the rotation of the projection lens 12 and an operation ofstoring the first boundary start angle, the first boundary angle, andthe first boundary end angle in the boundary storage unit 109, which areperformed before the projection of a desired content, will be referredto as an initial setting operation.

In addition, in the initial setting operation, the user, similarly tothe description presented above, designates a second boundary startangle that is a projection angle of a projection direction when theupper side of the projection image approximately coincides with theboundary between the floor face 222 and the wall face 220, a secondboundary angle that is a projection angle of a projection direction thatalmost coincides with the boundary between the floor face 222 and thewall face 220, and a second boundary end angle that is a projectionangle of a projection direction when the lower side of the projectionimage approximately coincides with the boundary between the floor face222 and the wall face 220, and the registration unit 118 stores thesecond boundary start angle, the second boundary angle, and the secondboundary end angle in the boundary storage unit 109 as well.

The keystone adjustment unit 107 illustrated in FIG. 4 sequentiallyreceives derived current projection angles 123 from the rotation controlunit 104. Then, the keystone adjustment unit 107, based on theinformation that is stored in the boundary storage unit 109, adjusts acorrection amount for a trapezoidal distortion for each of an anglerange for received projection angles 123 up to the first boundary startangle, an angle range from the first boundary start angle to the firstboundary angle, an angle range from the first boundary angle to thefirst boundary end angle, and an angle range after the first boundaryend angle. Similarly, the keystone adjustment unit 107, based on theinformation that is stored in the boundary storage unit 109, adjusts acorrection amount for a trapezoidal distortion for each of an anglerange for received projection angles 123 up to the second boundary startangle, an angle range from the second boundary start angle to the secondboundary angle, an angle range from the second boundary angle to thesecond boundary end angle, and an angle range after the second boundaryend angle.

Here, in shaping the shape of an image relating to the image data thatis a projection target from a rectangle to a trapezoid, the correctionamount for the trapezoidal distortion may be large in a case where adifference between the lengths of the upper side and the lower side ofthe shaped trapezoid is large, the correction amount for the trapezoidaldistortion may be small in a case where a difference between lengths ofthe upper side and the lower side of the shaped trapezoid is small. Thecorrection amount for the trapezoidal distortion may be increased in acase where the difference between the lengths of the upper side and thelower side of the shaped trapezoid increases, and the correction amountfor the trapezoidal distortion may be decreased in a case where thedifference between the lengths of the upper side and the lower side ofthe shaped trapezoid decreases.

The adjustment of the correction amount for the trapezoidal distortionthat is performed by the keystone adjustment unit 107 is performed basedon a correction coefficient derived in accordance with a projectionangle of each time.

Here, the correction coefficient may be derived based on the reciprocalof the ratio between the length of the upper side and the length of thelower side of the projection image that is projected so as to bedisplayed in a case where a trapezoidal correction is not performed.

Here, a case where the correction coefficient is “1” represents that thecorrection amount for a trapezoidal distortion is zero, in other words,the trapezoidal correction is not performed. In addition, as the valueof the correction coefficient becomes closer to “1”, the correctionamount for the trapezoidal distortion decreases, in other words, itrepresents that the degree of the trapezoidal correction decreases. Tothe contrary, as the value of the correction coefficient becomes fartherfrom “1”, the correction amount for the trapezoidal distortionincreases, in other words, it represents that the degree of thetrapezoidal correction increases. The process of adjusting thecorrection amount for the trapezoidal distortion based on the calculatedcorrection coefficient will be described later in detail.

The keystone adjustment unit 107 of the projector device 1 according tothis embodiment, for example, until the projection angle θ arrives atthe first boundary start angle from 0°, maintains the shape of theprojection image that is projected to the wall face 220 so as to bedisplayed thereon in an approximate rectangle and accordingly, anadjustment for increasing the correction amount for the trapezoidaldistortion is performed based on the correction coefficient derived inaccordance with the projection angle θ.

Next, the keystone adjustment unit 107 of the projector device 1, as theprojection angle θ changes from the first boundary start angle to thefirst boundary angle, performs an adjustment for decreasing thecorrection amount for the trapezoidal distortion based on the correctioncoefficient derived in accordance with the projection angle θ. Inaddition, the keystone adjustment unit 107, as the projection angle θchanges from the first boundary angle to the first boundary end angle,performs an adjustment for increasing the correction amount for thetrapezoidal distortion based on the correction coefficient derived inaccordance with the projection angle θ. In this way, in an angle rangeof the projection angle θ from the first boundary start angle to thefirst boundary end angle, the continuity of the shape of the projectionimage that is projected to the wall face 220 so as to be displayedthereon is maintained.

Then, the keystone adjustment unit 107 of the projector device 1, as theprojection angle θ increases to be larger than the first boundary endangle, in order to maintain the shape of the projection image that isprojected to the wall face 220 so as to be displayed thereon in anapproximate rectangle again, performs an adjustment for decreasing thecorrection amount for the trapezoidal distortion based on the correctioncoefficient derived in accordance with the projection angle θ.

Here, the keystone adjustment unit 107 determines the projectiondirection based on the projection angle θ and determines a correctiondirection of a trapezoidal correction performed for the trapezoidaldistortion based on the determination of the projection direction. Here,the correction direction represents which one of the upper side and thelower side of the image data is to be compressed. Then, the keystoneadjustment unit 107 derives each projection angle θ described above or acorrection coefficient for the angle range thereof based on thecorrection direction.

More specifically, in a case where the projection direction isdetermined to be a direction of the floor face or a direction upwardlyprojecting the wall face depending on the projection angle θ, the upperside of the trapezoid of the projection image displayed on theprojection face is longer than the lower side thereof, and accordingly,the keystone adjustment unit 107 determines the correction direction ofthe trapezoidal correction as a direction for compressing the upper sideof the trapezoid. Then, in a case where the correction direction of thetrapezoidal correction is determined as the direction for compressingthe upper side of the trapezoid, the keystone adjustment unit 107calculates the correction coefficient to be a positive value.

On the other hand, in a case where the projection direction isdetermined to be a direction downwardly projecting the wall face 220 ora direction for projecting the ceiling 221 based on the projection angle123, the lower side of the trapezoid of the projection image displayedon the projection face is longer than the upper side thereof, andaccordingly, the keystone adjustment unit 107 determines the correctiondirection of the trapezoidal correction as a direction for compressingthe lower side of the trapezoid. Then, in a case where the correctiondirection of the trapezoidal correction is determined as the directionfor compressing the lower side of the trapezoid, the keystone adjustmentunit 107 calculates the correction coefficient of the keystonecorrection to be a negative value.

The keystone correction unit 108 changes the lengths of the upper sideand the lower side of the image data corresponding to the upper side andthe lower side of the projection image that is projected to theprojection face so as to be displayed thereon based on the correctioncoefficient derived by the keystone adjustment unit 107 in accordancewith the projection angle θ, thereby performing the trapezoidalcorrection.

More specifically, in a case where the calculated correction coefficientis positive, the keystone correction unit 108 multiplies the length ofthe upper side of the image data by the correction coefficient, therebyperforming the trapezoidal correction for compressing the upper side. Onthe other hand, in a case where the calculated correction coefficient isnegative, the keystone correction unit 108 multiplies the length of thelower side of the image data by the correction coefficient, therebyperforming the trapezoidal correction for compressing the lower side.

FIGS. 17A and 17B are diagrams that illustrate a trapezoidal correctionperformed by the keystone correction unit 108 based on a correctionamount for a trapezoidal distortion that is derived by the keystoneadjustment unit 107 in a case where image data is projected to theprojection face illustrated in FIG. 16. In the example illustrated inFIGS. 17A and 17B, for the simplification of description, a case wherethe projection angle is increased from 0° to the upper side, in otherwords, a case where the position at which the projection image isprojected is moved from the wall face 220 to the ceiling 221 will bedescribed as an example. Thus, description of a keystone correctionaccording to the second boundary start angle, the second boundary angle,and the second boundary end angle will not be presented.

FIGS. 17A and 17B illustrate examples of the shapes of an image relatingto image data after the correction for a trapezoidal distortion isperformed by the keystone correction unit 108. Shapes 240, 241, 243,245, and 246 represented in FIG. 17A respectively illustrate imagesrelating to the image data that is projection target for the projectiondirections 230, 232, 231, 233, and 234 represented in FIG. 16. Inaddition, a shape 242 of an image illustrates the shape of an imagerelating to corresponding image data when the projection direction isbetween the projection direction 232 and the projection direction 231,and a shape 244 of an image illustrates the shape of an image relatingto corresponding image data when the projection direction is between theprojection direction 231 and the projection direction 233.

FIG. 17B illustrates an example of the shapes of a projection image thatis projected to a projection medium so as to be displayed thereon basedon image data after a correction for a trapezoidal distortion isperformed by the keystone correction unit 108. Shapes 250, 251, 253,255, and 256 represented in FIG. 17B respectively illustrate shapes ofprojection images projected to the projection medium in the projectiondirections 230, 232, 231, 233, and 234 represented in FIG. 16. Inaddition, a shape 252 illustrates the shape of a correspondingprojection image when the projection direction is between the projectiondirection 232 and the projection direction 231, and a shape 254illustrates the shape of a corresponding projection image when theprojection direction is between the projection direction 231 and theprojection direction 233.

The user, after the completion of the initial setting operation asdescribed above, rotates the projection lens 12 from the housed state tothe upper side while projecting an image relating to a desired content.In the case of the projection direction 230, which is in the initialstate, of a projection angle of 0°, as the shape 240 of an imagerelating to image data, a rectangular shape for which the correctioncoefficient is “1”, in other words, a correction amount for atrapezoidal distortion is zero is formed. Then, on the projection face,the projection image of the shape 250 that is a rectangle is displayed.

Thereafter, as the projection angle θ is increased, in order to maintainthe projection image displayed on the projection face to be in arectangle, the keystone adjustment unit 107 increases the correctionamount for a trapezoidal distortion by gradually decreasing thecorrection coefficient from “1”. In other words, as the projection angleθ is increased, the trapezoidal shape of the image relating to the imagedata is changed such that the length of the upper side is furthershorter than the length of the lower side.

Then, in a case where the projection angle is in the projectiondirection 232 corresponding to the first boundary start angle at whichthe upper side of the projection image almost coincides with theboundary between the wall face 220 and the ceiling 221, the shape 241 ofthe image relating to the image data, which is a trapezoidal shape forwhich the correction amount is largest in an angle range until theprojection angle arrives at the first boundary start angle from theinitial state, in other words, a trapezoidal shape in which a differencebetween the length of the upper side and the length of the lower side islargest in the angle range, is formed.

Thereafter, the keystone adjustment unit 107 performs an adjustment fordecreasing a correction amount for a trapezoidal distortion, compared tothe case of the shape 241, by causing the correction coefficient togradually approach “1”, and a trapezoidal correction is performed by thekeystone correction unit 108. In other words, the keystone correctionunit 108 gradually cancels the trapezoidal correction for the image databy decreasing the correction amount by using the keystone adjustmentunit 107 for a trapezoidal correction in the case of the first boundarystart angle. In the example illustrated in FIGS. 17A and 17B, comparedto the shape 241 of the image relating to the image data, thetrapezoidal correction for the shape 242 of the image relating to theimage data is canceled, whereby a difference between the length of theupper side and the length of the lower side is decreased.

Then, in a case where the projection angle θ is the first boundary anglecorresponding to the projection direction 231, in other words, thedirection of the boundary (the boundary 231 b in each of shapes 252 to254 in FIG. 17B) between the wall face 220 and the ceiling 221, thekeystone adjustment unit 107 sets the correction amount for atrapezoidal distortion to zero by setting the correction coefficient to“1” (“−1”), in other words, completely cancels the trapezoidalcorrection for the image data and projects an image having the shape 243relating to the image data having a rectangular shape again.

Thereafter, as the projection angle θ passes through the first boundaryangle and is increased, the keystone adjustment unit 107 graduallyincreases the correction amount for a trapezoidal distortion bygradually increasing the correction coefficient from “−1”. In otherwords, in a trapezoidal shape of an image relating to the image data, asthe projection angle θ increases, the length of the lower side changesto be longer than the length of the upper side. In addition, at thistime, since the correction coefficient is gradually increased from “−1”,the keystone correction unit 108 performs a trapezoidal correction basedon a correction direction that is opposite to that of the trapezoidalcorrection used for a projection image to be projected to the wall face.

Then, in a case where the projection angle θ is in the projectiondirection 233 corresponding to the first boundary end angle at which thelower side (a side disposed farther from the projector device 1) of theprojection image almost coincides with the boundary between the wallface 220 and the ceiling 221, the shape 241 of the image relating to theimage data, which has a trapezoidal shape for which the correctionamount is largest in an angle range until the projection angle θ arrivesat 90° from the first boundary end angle, in other words, a trapezoidalshape in which a difference between the length of the upper side and thelength of the lower side is largest in the range, is formed.

In the way described above, in the angle range in which the projectionangle θ is larger than the first boundary start angle and is smallerthan the first boundary end angle, the shape of the projection imagethat is projected to the projection medium so as to be displayed thereoncan be continuously changed. In other words, in this angle range, aprojection image is displayed in which, while a shape having atrapezoidal portion of which the upper side is longer than the lowerside on the wall face and having a trapezoidal portion of which theupper side is shorter than the lower side at the ceiling is maintained,only the lengths of lower side of the trapezoidal portion formed on thewall face and the upper side of the trapezoidal portion formed at theceiling, and the height of each trapezoid are continuously changed.

Then, in a case where the projection angle becomes 90° corresponding tothe projection direction 234, in other words, a direction right abovethe projector device 1 of the ceiling 221, a rectangular shape for whichthe correction coefficient is “1”, in other words, the correction amountfor a trapezoidal distortion is zero is formed as the shape 246 of theimage relating to the image data. Then, on the projection face, aprojection image having the shape 256 of the rectangle is displayed.

In addition, the projection lens 12 may be rotated toward the rear face,and, as the correction operation, a correction opposite to thecorrection of the projection direction 230 to the projection direction234 may be performed.

In the way described above, according to the projector device 1, even ina case where the display position of the projection image that isprojected so as to be displayed passes through the boundary of the firstprojection face and the second projection face lined up to have apredetermined angle therebetween and changes, a smooth and stable imagethat can be easily viewed can be displayed to an observer.

In addition, in the above-described example, the process has beendescribed in which, in the angle range of the projection direction 232in which the projection angle θ is the first boundary start angle to theprojection direction 231 in which the projection angle θ is an anglecorresponding to the boundary, the correction amount for a trapezoidaldistortion is gradually decreased as the projection angle θ increases,and, in the angle range of the projection direction 231 in which theprojection angle θ is an angle (first boundary angle) corresponding tothe boundary to the projection direction 233 in which the projectionangle θ is the first boundary end angle, the correction amount for atrapezoidal distortion is gradually increased as the projection angle θincreases.

Meanwhile, when the projection angle θ is in an angle range of the firstboundary start angle to the first boundary end angle, the keystoneadjustment unit 107 may completely cancel the trapezoidal correction bysetting the correction amount to zero. Also in such a case, in the anglerange of the projection angle θ from the first boundary start angle tothe first boundary end angle, the shape of the projection imagedisplayed on the projection face that is formed by the wall face and theceiling can be continuously changed. In addition, in the angle range ofthe projection angle θ from the first boundary start angle to the firstboundary end angle, the correction amount may be a correction amount forone of the first boundary start angle and the first boundary end angle.Also in such a case, in the angle range of the projection angle θ fromthe first boundary start angle to the first boundary end angle, theshape of the projection image displayed on the projection face that isformed by the wall face and the ceiling can be continuously changed.

Next, the relation between the projection angle and the correctioncoefficient and the correction coefficient and the correction amount fora trapezoidal distortion that are derived in accordance with theprojection angle will be described in detail. FIG. 18 is a diagram thatillustrates major projection directions and projection angles θaccording to the first embodiment. Here, the projection directions 230,232, 231, 233, and 234 are common to FIGS. 18 and 16.

Here, the projection angle θ is an inclination angle of the optical axisof projection light emitted from the projection lens 12 with respect tothe horizontal direction. Hereinafter, an inclination angle of a casewhere the optical axis of the projection light is in the horizontaldirection is set as 0°, a case where the drum unit 10 including theprojection lens 12 is rotated to the upper side, in other words, theelevation angle side will be defined as positive, and a case where thedrum unit 10 is rotated to the lower side, in other words, thedepression angle side will be defined as negative. In such a case, ahoused state in which the optical axis of the projection lens 12 faces afloor face disposed right below corresponds to a projection angle of−90°, and a horizontal state in which the projection direction faces thefront side of a wall face 220 corresponds to a projection angle of 0°,and a state in which the projection direction faces a ceiling 221disposed right above corresponds to a projection angle of +90°.

In the example illustrated in FIG. 18, the projection angle θ at thetime of the projection direction 230 is 0°, the projection angle θ atthe time of the projection direction 232 is 35°, the projection angle θat the time of the projection direction 231 is 42°, and, the projectionangle θ at the time of the projection direction 233 is 49°.

A projection direction 235 is a direction in which projection is startedby the projector device 1 that is acquired by rotating the projectionlens from a state in which the projection lens is positioned toward theright below side)(−90°, and the projection angle θ at this time is −45°.A projection direction 236 is the projection direction of the projectionlens in a case where an upper face, which corresponds to a first side,of one pair of sides disposed in a direction perpendicular to the movingdirection of a projection image approximately coincides with a boundarybetween the floor face 222 and the wall face 220 in the projection imageon the floor face 222. The projection angle θ at this time will bereferred to as a second boundary start angle, and the second boundarystart angle is −19°.

A projection direction 237 is a direction of a boundary between thefloor face 222 and the wall face 220 that are two projection facesadjacent to each other. The projection angle θ at this time will bereferred to as a second boundary angle, and the second boundary angle is−12°.

A projection direction 238 is the projection direction of the projectionlens in a case where a lower face, which corresponds to a second side,of the above-described one pair of sides of the projection image on thewall face 220 approximately coincides with a boundary between the floorface 222 and the wall face 220. The projection angle θ at this time willbe referred to as a second boundary end angle, and the second boundaryend angle is −4°.

FIG. 19 is a graph that illustrates a relation between the projectionangle and the correction coefficient according to the first embodiment.In FIG. 19, the horizontal axis represents the projection angle θ, andthe vertical axis represents the correction coefficient. The correctioncoefficient takes a positive value or a negative value. As describedabove, in a case where the correction coefficient is positive, itrepresents a correction direction for compressing the length of theupper side of the trapezoid of the image data. On the other hand, in acase where the correction coefficient is negative, it represents acorrection direction for compressing the length of the lower side of thetrapezoid of the image data. In addition, as described above, in a casewhere the correction coefficient is “1” or “−1”, the correction amountfor the trapezoidal distortion is zero, whereby the trapezoidalcorrection is completely canceled.

In FIG. 19, the projection directions 235, 236, 237, 238, 230, 232, 231,233, and 234 illustrated in FIG. 18 are illustrated in association withprojection angles θ thereof. As illustrated in FIG. 19, in a range 260from a projection angle (−45°) for the projection direction 235 to aprojection angle (−12°) for the projection direction 237, the projectionlens projects the floor face 222.

In addition, as illustrated in FIG. 19, in a range 261 from a projectionangle (−12°) for the projection direction 237 to a projection angle (0°)for the projection direction 230, the projection lens projects the wallface 220 downward. Furthermore, as illustrated in FIG. 19, in a range262 from a projection angle (0°) for the projection direction 230 to aprojection angle (42°) for the projection direction 231, the projectionlens projects the wall face 220 upward.

In addition, as illustrated in FIG. 19, in a range 263 from a projectionangle (42°) for the projection direction 231 to a projection angle (90°)for the projection direction 234, the projection lens projects theceiling 221.

The keystone adjustment unit 107 derives a trapezoidal distortioncorrection amount based on a correction coefficient according to eachprojection angle θ denoted by a solid line in FIG. 19 and performs atrapezoidal correction for the image data based on the calculatedcorrection amount. In other words, the keystone adjustment unit 107,based on the projection angle, determines whether the projectiondirection of the projection lens 12 is the projection direction that isan upward projection direction with respect to the wall face 220, theprojection direction toward the face of the ceiling 221, the projectiondirection that is a downward direction for the wall face 220, or theprojection direction toward the floor face 222 and determines acorrection direction for the image data in accordance with theprojection direction. Then, the keystone adjustment unit 107 derives acorrection coefficient corresponding to the projection angle 123 that isoutput from the rotation control unit 104.

Here, as illustrated in FIG. 19, between a projection angle (−45°) atthe time of the projection direction 235 and the second boundary startangle (−19°) that is the projection angle at the time of the projectiondirection 236 and between a projection angle (0°) at the time of theprojection direction 230 and the first boundary start angle (35°) thatis the projection angle at the time of the projection direction 232, thecorrection coefficient is positive and gradually decreases, and thecorrection amount for the trapezoidal distortion gradually increases.Here, the correction coefficient or the correction amount therebetweenis used for maintaining the shape of the projection image projected ontothe projection face to be a rectangle.

On the other hand, as illustrated in FIG. 19, between the secondboundary start angle (−19°) that is the projection angle at the time ofthe projection direction 236 and the second boundary angle (−12°) thatis the projection angle at the time of the projection direction 237 andbetween the first boundary start angle (35°) that is the projectionangle of the projection direction 232 and the first boundary angle (42°)that is the projection angle at the time of the projection direction231, the correction coefficient is positive and gradually increases, anda correction amount for a trapezoidal distortion is gradually decreased.

The correction coefficient of the conventional projector device 3100described above therebetween is denoted by broken lines in FIG. 19. Inthe conventional projector device 3100, also after the second boundaryangle (−19°) that is the projection angle at the time of the projectiondirection 236 or the first boundary angle (35°) that is the projectionangle at the time of the projection direction 232, in a case where theprojection medium is formed not by two projection faces having apredetermined angle therebetween but by only one projection face, inorder to maintain the shape of the projection image projected to theprojection face to be a rectangle, the correction coefficient is set tobe positive and gradually decreases, and the correction amount for atrapezoidal distortion is gradually increased.

In contrast to this, in the projector device 1 according to thisembodiment, as described above, the correction coefficient is positiveand gradually increases, and the correction amount for a trapezoidaldistortion gradually decreases. Here, this increase may not be a graduallinear increase as illustrated in FIG. 19 but may be an exponentialincrease or a geometric increase as long as the increase is a continuousgradual increase therebetween.

In addition, as illustrated in FIG. 19, between the second boundaryangle (−12°) that is the projection angle at the time of the projectiondirection 237 and the second boundary end angle (−4°) that is theprojection angle at the time of the projection direction 238 and betweenthe first boundary angle (42°) that is the projection angle of theprojection direction 231 and the first boundary end angle (49°) that isthe projection angle θ at the time of the projection direction 233, thecorrection coefficient is negative and gradually increases, and thecorrection amount for the trapezoidal distortion is gradually increased.

The correction coefficient of the conventional projector device 3100described above therebetween is denoted by broken lines in FIG. 19. Inthe conventional projector device 3100, also after the second boundaryangle (−12°) that is the projection angle at the time of the projectiondirection 237 or the first boundary angle (42°) that is the projectionangle at the time of the projection direction 231, in a case where theprojection medium is formed not by two projection faces having apredetermined angle therebetween but by only one projection face, inorder to maintain the shape of the projection image projected to theprojection face to be a rectangle, the correction coefficient is set tobe negative and gradually decreases, and the correction amount for atrapezoidal distortion is gradually decreased.

In contrast to this, in the projector device 1 according to thisembodiment, as described above, the correction coefficient is negativeand is gradually increased, and the correction amount for a trapezoidaldistortion is gradually increased. Here, this increase may not be agradual linear increase as illustrated in FIG. 19 but may be anexponential increase or a geometric increase as long as the increase isa continuous gradual increase therebetween.

On the other hand, as illustrated in FIG. 19, between the secondboundary end angle (−4°) that is the projection angle at the time of theprojection direction 238 and the projection angle (0°) at the time ofthe projection direction 230 and between the first boundary end angle(49°) that is the projection angle of the projection direction 233 andthe projection angle (90°) at the time of the projection direction 234,the correction coefficient is negative and gradually decreases, and acorrection amount for a trapezoidal distortion is gradually decreased.Here, the correction coefficient or the correction amount therebetweenis used for maintaining the shape of the projection image projected ontothe projection face to be a rectangle.

Here, a technique for calculating the correction coefficient will bedescribed. FIG. 20 is a diagram that illustrates the calculation of thecorrection coefficient. The correction coefficient is the reciprocal ofa ratio between the upper side and the lower side of a projection imagethat is projected to the projection medium so as to be displayed thereonand is the same as d/e that is a ratio between lengths d and e in FIG.20. Accordingly, in the trapezoidal distortion correction, the upperside or the lower side of the image data is reduced by d/e times.

Here, as illustrated in FIG. 20, when a ratio of a distance a from theprojector device 1 to a lower side of the projection image that isprojected to the projection medium so as to be displayed thereon to adistance b from the projector device 1 to an upper side of theprojection image is represented as a/b, d/e is represented in thefollowing Equation (10).

$\begin{matrix}{\frac{d}{e} = \frac{a}{b}} & (10)\end{matrix}$

Then, in FIG. 20, when a value θ is the projection angle, a value β is ahalf of the view angle α, and a value n is a projection distance fromthe projector device 1 to the wall face in the horizontal direction, thefollowing Equation (11) is formed.n=b cos(θ+β)=a cos(θ−β)  (11)

By transforming Equation (11), Equation (12) is derived. Accordingly,based on Equation (12), the correction coefficient is determined basedon the angle β that is a half of the view angle α and the projectionangle θ.

$\begin{matrix}\begin{matrix}{\frac{a}{b} = \frac{\cos\left( {\theta + \beta} \right)}{\cos\left( {\theta - \beta} \right)}} \\{= {k\left( {\theta,\beta} \right)}}\end{matrix} & (12)\end{matrix}$

Based on this Equation (12), in a case where the projection angle θ is0°, in other words, in a case where the projection image is projectedonto the wall face 220 in a horizontal direction, the correctioncoefficient is “1”, and, in such a case, the trapezoidal distortioncorrection amount is zero.

In addition, based on Equation (12), the correction coefficientdecreases as the projection angle θ increases, and the correction amountfor a trapezoidal distortion increases according to the value of thecorrection coefficient. Accordingly, the trapezoidal distortion of theprojection image that becomes remarkable according to an increase in theprojection angle θ can be appropriately corrected.

Furthermore, in a case where the projection image is projected to theceiling 221, the correction direction of the keystone correctionchanges, and accordingly, the correction coefficient is b/a. Inaddition, as described above, the sign of the correction coefficient isnegative.

In the conventional technology, the correction coefficients for all theprojection angles are calculated using Equation (12). The correctioncoefficient denoted by the dotted lines in FIG. 19 is based on thisEquation (12). The calculation of the correction coefficient accordingto the conventional technology will be described in detail withreference to FIG. 33.

FIG. 33 is a graph that illustrates a relation among the projectionangle, the view angle, and the correction coefficient according to aconventional technology that is based on Equation (12). For example, inthe case of a view angle of 14 degrees (β=±7 degrees), in theconventional projector device, a correction coefficient is acquiredaccording to a curve of a view angle β of ±7 degrees illustrated in FIG.33, and a keystone correction is performed for the image data.

In the projector device 1 according to this embodiment, the keystoneadjustment unit 107 calculates a correction coefficient using Equation(12) in the range of a part of projection angles, and, in a range otherthan the part, Equation (12) is not used, and a correction coefficientis derived so as to be gradually increased or gradually decreasedcontinuously in the range.

In this embodiment, the keystone adjustment unit 107 calculates thecorrection coefficient based on Equation (12) when the projection angleis between the projection angle (−45°) at the time of the projectiondirection 235 and the second boundary start angle (−19°) that is theprojection angle at the time of the projection direction 236, betweenthe projection angle (0°) at the time of the projection direction 230and the first boundary start angle (35°) that is the projection angle atthe time of the projection direction 232, between the second boundaryend angle (−4°) that is the projection angle at the time of theprojection direction 238 and the projection angle (0°) at the time ofthe projection direction 230, or between the first boundary end angle(49°) that is the projection angle of the projection direction 233 andthe projection angle (90°) at the time of the projection direction 234,described above.

On the other hand, the keystone adjustment unit 107 derives thecorrection coefficient so as to gradually increase within the rangewithout using Equation (12) when the projection angle is between thesecond boundary start angle (−19°) that is the projection angle at thetime of the projection direction 236 and the second boundary angle(−12°) that is the projection angle at the time of the projectiondirection 237 or between the first boundary start angle (35°) that isthe projection angle of the projection direction 232 and the firstboundary angle (42°) that is the projection angle at the time of theprojection direction 231. In such a case, the correction amount isgradually decreased.

In addition, the keystone adjustment unit 107 derives the correctioncoefficient so as to continuously gradually increase in the rangewithout using Equation (12) also when the projection angle is betweenthe second boundary angle (−12°) that is the projection angle at thetime of the projection direction 237 and the second boundary end angle(−4°) that is the projection angle at the time of the projectiondirection 238 or between the first boundary angle (42°) that is theprojection angle at the time of the projection direction 231 and thefirst boundary end angle (49°) that is the projection angle at the timeof the projection direction 233. In such a case, the correction amountis gradually increased.

The keystone correction unit 108 multiplies the length H_(act) of theline of the upper side of the image data by a correction coefficientk(θ, β) represented in Equation (12) and calculates the lengthH_(act)(θ) of the line of the upper side after the correction using thefollowing Equation (13).H _(act)(θ)=k(θ,β)×H _(act)  (13)

The keystone correction unit 108, in addition to the length of the upperside of the image data, calculates the length of each line in a rangefrom the line of the upper side to the line of the lower side andperforms a correction. FIG. 21 is a diagram that illustrates thecalculation of lengths of lines from the upper side to the lower side.

As illustrated in FIG. 21, the keystone correction unit 108 calculatesand corrects the length H_(act)(y) of each line from the upper side tothe lower side of the image data so as to be linear using the followingEquation (14). Here, V_(act) is the height of the image data, in otherwords, the number of lines, and Equation (14) is an equation forcalculating the length H_(act)(y) of the line at a position y from theupper side.

$\begin{matrix}{{H_{act}(y)} = {\left\{ {1 - {\left( {1 - {k\left( {\theta,\beta} \right)}} \right) \times \frac{V_{act} - y}{V_{act}}}} \right\} \times H_{act}}} & (14)\end{matrix}$

Flow of Process for Projecting Image Data

Next, the flow of the process performed when an image according to theimage data is projected by the projector device 1 will be described.FIG. 22 is a flowchart that illustrates the sequence of an imageprojection process according to the first embodiment.

In step S100, in accordance with input of image data, various settingvalues relating to the projection of an image according to the imagedata are input to the projector device 1. The input various settingvalues, for example, are acquired by the input control unit 119 and thelike. The various setting values acquired here, for example, include avalue representing whether or not the image according to the image datais rotated, in other words, whether or not the horizontal direction andthe vertical direction of the image are interchanged, an enlargementrate of the image, and an offset angle θ_(ofst) at the time ofprojection. The various setting values may be input to the projectordevice 1 as data in accordance with the input of the image data to theprojector device 1 or may be input by operating the operation unit 14.

In next step S101, image data corresponding to one frame is input to theprojector device 1, and the input image data is acquired by the imagecut-out unit 100. The acquired image data is written into the memory101.

In next step S102, the image control unit 103 acquires the offset angleθ_(ofst). In next step S103, the image control unit 103 acquires the cutout size, in other words, the size of the cut out area of the inputimage data. The image control unit 103 may acquire the size of the cutout area based on a setting value acquired from step S100 or may acquirethe size of the cut out area in accordance with an operation for theoperation unit 14. In next step S104, the image control unit 103acquires the view angle α of the projection lens 12. The image controlunit 103 acquires the view angle α of the projection lens 12, forexample, from the view angle control unit 106. In addition, in next stepS105, the image control unit 103 acquires the projection angle θ of theprojection lens 12, for example, from the rotation control unit 104.

In the next step S106, the image control unit 103 acquires the cut outarea for the input image data based on the offset angle θ_(ofst), thesize of the cut out area, the view angle α, and the projection angle θacquired in steps S102 to S105 by using Equations (3) to (8) describedabove. The image control unit 103 instructs the image cut-out unit 100to read image data from the acquired cut out area. The image cut-outunit 100 reads image data within the cut out area from the image datastored in the memory 101 in accordance with the instruction from theimage control unit 103. The image cut-out unit 100 supplies the imagedata of the cut out area read from the memory 101 to the imageprocessing unit 102.

In step S107, the image processing unit 102, for example, performs asize converting process according to Equations (1) and (2) describedabove for the image data supplied from the image cut-out unit 100. Then,in step S108, a trapezoidal correction is performed for the image datafor which the size converting process has been performed by the imageprocessing unit 102. More specifically, as described above, the keystoneadjustment unit 107 derives the correction coefficient in accordancewith the projection angle, and the keystone correction unit 108multiplies the length of the upper side or the lower side of the imagedata output from the image processing unit 102 by the derived correctioncoefficient, whereby the trapezoidal correction is performed.

The image data for which the trapezoidal correction has been performedby the keystone correction unit 108 is supplied to the display element114. The display element 114 modulates light emitted from the lightsource 111 in accordance with the image data and emits modulated light.The emitted light is projected from the projection lens 12.

In next step S109, the image cut-out unit 100 determines whether or notan input of image data of a next frame after the image data input instep S101 described above is present. In a case where the input of theimage data of the next frame is determined to be present, the imagecut-out unit 100 returns the process to step S101 and performs theprocess of steps S101 to S108 described above for the image data of thenext frame. In other words, the process of steps S101 to S108 isrepeated in units of frames of the image data, for example, inaccordance with a vertical synchronization signal VD of the image data.Accordingly, the projector device 1 can cause each process to follow achange in the projection angle θ in units of frames.

On the other hand, in step S109, in a case where the image data of thenext frame is determined not to have been input, a control unit (notillustrated in the figure) controlling the overall operation of thedevice stops the image projection operation in the projector device 1.For example, the control unit (not illustrated in the figure) controlsthe light source 111 so as to be turned off and issues a command forreturning the posture of the drum unit 10 to be in the housed state tothe rotation mechanism unit 105. Then, after the posture of the drumunit 10 is returned to be in the housed state, the control unit (notillustrated in the figure) stops the fan cooling the light source 111and the like.

Here, a specific trapezoidal correction operation will be described. Itis assumed that the initial setting operation has been completed inadvance, and the first boundary start angle, the first boundary angle,the first boundary end angle, the second boundary start angle, thesecond boundary angle, and the second boundary end angle are registeredin the boundary storage unit 109.

When power is input to the projector device 1, the projection lens 12 isrotated, and a projection image is projected onto the floor face fromthe projection direction 235 (−45°), and the trapezoidal correction isperformed. The projection angle passes through the second boundary startangle (−19°) that is the projection angle for the projection direction236 at the time when the upper side of the projection image arrives atthe boundary between the floor face 222 and the wall face 220 and thesecond boundary angle (−12°) that is the projection angle for theprojection direction 237 of the boundary between the floor face 222 andthe wall face 220 and arrives at the second boundary end angle (−4°)that is the projection angle for the projection direction 238 at thetime when the lower side of the projection image arrives at the boundarybetween the floor face 222 and the wall face 220.

During the period, the keystone adjustment unit 107 and the keystonecorrection unit 108 gradually decrease the correction amount for atrapezoidal distortion from the second boundary start angle at which theprojection angle θ corresponds to the projection direction 236, and thecorrection amount for a trapezoidal distortion is set to zero when theprojection angle θ is the second boundary angle corresponding to theprojection direction 237.

The keystone adjustment unit 107 and the keystone correction unit 108set the correction coefficient to “−1” from when the projection angle θexceeds the second boundary angle and gradually increase the correctionamount for a trapezoidal distortion, and the projection angle arrives atthe second boundary end angle corresponding to the projection direction238. The keystone adjustment unit 107 and the keystone correction unit108 decrease the correction amount for a trapezoidal distortion suchthat the projection image is maintained to be in a rectangular shapefrom when the projection angle θ is the second boundary end anglecorresponding to the projection direction 238 to when the projectionangle θ is a projection angle (0°) corresponding to the projectiondirection 230 and set the correction amount for a trapezoidal distortionto zero when the projection angle becomes the projection angle θcorresponding to the projection direction 230.

The keystone adjustment unit 107 and the keystone correction unit 108increase the correction amount for a trapezoidal distortion from a timepoint when the projection angle θ exceeds a projection angle (0°)corresponding to the projection direction 230 such that the projectionimage is maintained to be in a rectangular shape, and the projectionangle arrives at the first boundary start angle (35°) that is theprojection angle θ corresponding to the projection direction 232 whenthe upper side of the projection image arrives at the boundary betweenthe wall face 220 and the ceiling 221. The keystone adjustment unit 107and the keystone correction unit 108 gradually decrease the correctionamount for a trapezoidal distortion from when the projection angle θ isthe first boundary start angle corresponding to the projection direction232 and set the correction amount for a trapezoidal distortion to zerowhen the projection angle θ becomes the first boundary angle (42°)corresponding to the projection direction 231 toward the boundarybetween the wall face 220 and the ceiling 221.

The keystone adjustment unit 107 and the keystone correction unit 108set the correction coefficient to “−1” from when the projection angle θexceeds the first boundary angle and gradually increase the correctionamount for a trapezoidal distortion, and the projection angle arrives atthe first boundary end angle (49°) corresponding to the projectiondirection 233 at the time when the lower side of the projection imagearrives at the boundary between the wall face 220 and the ceiling 221.The keystone adjustment unit 107 and the keystone correction unit 108decrease the correction amount for a trapezoidal distortion such thatthe projection image is maintained to be in a rectangular shape from thefirst boundary end angle corresponding to the projection direction 233to a projection angle (90°) corresponding to the projection direction234 and set the correction amount for a trapezoidal distortion to zeroat a projection angle (90°) corresponding to the projection direction234.

Thereafter, the keystone adjustment unit 107 and the keystone correctionunit 108 may perform the same correction until the projection anglebecomes a projection angle of 225° exceeding the projection angle θcorresponding to the projection direction 234 or may additionallyvertically reverse the projection image.

As above, according to this embodiment, the keystone adjustment unit 107and the keystone correction unit 108 gradually decrease the correctionamount for a trapezoidal distortion when the projection angle θ of theprojection lens 12 is between the boundary start angle of the projectiondirection at which the upper side of the projection image approximatelycoincides with the boundary of two projection faces adjacent to eachother and the boundary angle of the projection direction toward theboundary. Then, when the projection angle is between the boundary angleand the boundary end angle corresponding to the projection direction inwhich the lower side of the projection image approximately coincideswith the above-described boundary, the correction amount for atrapezoidal distortion is gradually increased. Accordingly, the shape ofthe projection image that is projected is continuously changed, and alsoat the boundary between the two projection faces, the smooth and stableprojection image that can be easily viewed can be displayed.

First Modified Example of First Embodiment

In the first embodiment, in a case where the projection direction of theprojection lens 12 corresponds to the first boundary angle correspondingto the projection direction 231 toward the boundary between the wallface 220 and the ceiling 221 or the second boundary angle correspondingto the projection direction 237 toward the boundary between the floorface 222 and the wall face 220, the correction coefficient is set to “1”or “−1”, whereby the trapezoidal distortion correction is canceled.

However, in a first modified example of the first embodiment, thetrapezoidal distortion correction is configured to be canceled bysetting the correction coefficient to “1” or “−1” in a case where theprojection angle θ becomes an angle near the first boundary angle or anangle near the second boundary angle instead of at a time point when theprojection angle θ becomes precisely the first boundary angle or thesecond boundary angle.

FIG. 23 is a diagram that illustrates major projection directions andprojection angles θ of a projection face according to the first modifiedexample. FIG. 24 is a graph that illustrates a relation between aprojection angle θ and a correction coefficient according to the firstmodified example. In this modified example, the keystone adjustment unit107, as illustrated in FIGS. 23 and 24, the correction coefficient isset to “1” or “−1” at a projection angle θ corresponding to a projectiondirection 231′ toward a position slightly deviated from the boundarybetween the wall face 220 and the ceiling 221 and a projection angle θcorresponding to a projection direction 237′ toward a position slightlydeviated from the boundary between the floor face 222 and the wall face220.

In other words, the keystone adjustment unit 107, as illustrated in FIG.24, in a range of the projection angle θ from the projection direction236 to the projection direction 238 and a range from the projectiondirection 232 to the projection direction 233, is configured togradually increase the correction coefficient in accordance with anincrease in the projection angle θ. By setting the correctioncoefficient to “1” or “−1” at a position near the boundary that is notprecisely located at the boundary, the same advantages as those of thefirst embodiment can be acquired.

Second Modified Example of First Embodiment

According to the first embodiment, in the initial setting operation, thefirst boundary start angle, the first boundary angle, the first boundaryend angle, the second boundary start angle, the second boundary angle,and the second boundary end angle are designated by the user and arestored in the boundary storage unit 109 by the registration unit 118.

However, by allowing the user to designate some of all the angles, theother angles may be calculated using the view angle α of the projectionimage.

As such a second modified example, for example, in the initial settingoperation, a first boundary start angle at a time when the upper side ofthe projection image approximately coincides with the boundary betweenthe wall face 220 and the ceiling 221 and a second boundary start angleat a time when the upper side of the projection image approximatelycoincides with the boundary between the floor face 222 and the wall face220 are designated by the user pressing keys of the operation unit 14,and the other projection angles θ are not designated by the user.

Accordingly, the registration unit 118 stores the first boundary startangle and the second boundary start angle in the boundary storage unit109. In addition, since the view angle α is an angle that is formed bythe upper side of the projection image, the projection lens 12, and thelower side of the projection image, the registration unit 118, by usingthe view angle α, can calculate the first boundary angle at which theboundary between the wall face 220 and the ceiling 221 is the projectiondirection 231 and the first boundary end angle corresponding to theprojection direction 233 in which the lower side of the projection imageapproximately coincides with the boundary between the wall face 220 andthe ceiling face 221 based on the first boundary start angle and storethe calculated angles in the boundary storage unit 109. To the contrary,by allowing the user to designate the first boundary end angle, theregistration unit 118 may be configured to calculate the first boundarystart angle based on the first boundary end angle and the view angle α.

Similarly, the registration unit 118, by using the view angle α, cancalculate the second boundary angle at which the boundary between thefloor face 222 and the wall face 220 is the projection direction 237 andthe second boundary end angle corresponding to the projection direction238 in which the lower side of the projection image approximatelycoincides with the boundary between the floor face 222 and the wall face220 based on the second boundary start angle and store the calculatedangles in the boundary storage unit 109. To the contrary, by allowingthe user to designate the second boundary end angle, the registrationunit 118 may be configured to calculate the second boundary start anglebased on the second boundary end angle and the view angle α.

In addition, in the initial setting operation, the user is allowed todesignate two angles including the first boundary start angle and thefirst boundary end angle, and the two angles are registered in theboundary storage unit 109, and, the registration unit 118 may beconfigured to calculate the first boundary angle by using one of theangles and the view angle α and store the calculated first boundaryangle in the boundary storage unit 109. The calculation of the secondboundary angle may be similarly performed.

Alternatively, in the initial setting operation, only the first boundaryangle is designated by the user and is registered in the boundarystorage unit 109, and the registration unit 118 may be configured tocalculate the first boundary start angle and the first boundary endangle based on the first boundary angle and the view angle α and storethe calculated angles in the boundary storage unit 109. The calculationof the second boundary start angle and the second boundary end angle maybe similarly performed.

According to this second modified example, the same advantages as thoseof the first embodiment are acquired. In addition, in the initialsetting operation, all the projection angles θ of the first boundarystart angle, the first boundary angle, the first boundary end angle, thesecond boundary start angle, the second boundary angle, and the secondboundary end angle do not need to be registered by the user, wherebyuser convenience is improved.

In addition, similarly to the first modified example, in a case wherethe correction coefficient is adjusted to “1” or “−1’ at a positionslightly deviated from the boundary, it may be configured such that onlythe first boundary start angle is designated by the user, and the firstboundary end angle is calculated by the registration unit 118 based onthe first boundary start angle and the view angle α.

Second Embodiment

In the first embodiment and the modified examples thereof, while thedrum unit 10 is rotated in the vertical direction, and the projectionarea is changed in the vertical direction in accordance with theprojection angle θ according to the projection lens 12, the presentinvention is not limited thereto. In a second embodiment, the projectionarea according to the projection lens 12 can be changed in thehorizontal direction.

FIG. 25 is a diagram that illustrates an example of an external view ofa projection device (projector device) 1′ according to the secondembodiment. FIG. 25 illustrates a state in which a cover and the like ofthe projection device 1′ are removed. The same reference numeral isassigned to each portion common to FIGS. 1A and 1B and FIGS. 2A and 2Bdescribed above, and detailed description thereof will not be presented.

In the projector device 1′, a horizontal rotation casing 300 is attachedto a turntable 301. To the horizontal rotation casing 300, a drum 30having a projection lens 12 on the inside thereof is attached to berotatable around a shaft unit 38 as its center in the verticaldirection. In accordance with the rotation of the turntable 301, thehorizontal rotation casing 300 is rotated in the horizontal direction,and, in accordance therewith, a projection direction according to theprojection lens 12 is changed in the horizontal direction.

FIG. 26 illustrates an example of the external view of a base 302. Thebase 302 includes the turntable 301. A gear 304 is attached to the rearside of the turntable 301. The turntable 301 is configured to be rotatedaround a shaft 303 as its center in the horizontal direction inaccordance with rotation that is transferred from a drive unit to bedescribed later through the gear 304. In addition, inside the base 302,various substrates of a circuit unit, a power supply unit, and the likeare disposed. Furthermore, on one of side faces of the base 302, anoperation unit (not illustrated in the figure) is disposed. The sideface of the base 302 on which the operation unit is disposed will bereferred to as a first face.

FIG. 27 is a diagram that illustrates the turntable 301 seen from therear face side. A drive unit 313 transfers rotation to the gear 304,thereby rotating the turntable 301. More specifically, the drive unit313 includes a motor 320 that is, for example, a stepping motor and agear group including a worm gear 321 that is directly driven by therotation shaft of the motor 320, a gear 322 that transfers rotationaccording to the worm gear 321, and a gear 323 that transfers therotation transferred from the gear 322 to the gear 304 of the turntable301. By transferring the rotation of the motor 320 to the gear 304 usingthe gear group, the turntable 301 can be rotated in accordance with therotation of the motor 320. The rotation speed of the turntable 301 isdetermined based on the rotation speed of the motor 320 and the gearratio of the gear group.

In the turntable 301, protrusions 312 a and 312 b are disposed. Bydetecting the protrusions 312 a and 312 b using a photo interrupter notillustrated in the figure or the like, the direction of the turntable301 with respect to a reference direction can be acquired.

In this second embodiment, for the convenience of description and easyunderstanding, it is assumed that the drum 30 is not rotated in thevertical direction, and the projection lens 12 is rotated in thehorizontal direction in accordance with the rotation of the turntable301. In a case where the projection direction of the projection lens 12faces toward the vertical direction with respect to the side face (firstface) having the operation unit of the base 302, the projection angleaccording to the projection lens 12 in the horizontal direction is 0°,and the posture having a projection angle of 0° forms the initial state.The projection angle according to the projection lens 12 increases inthe counterclockwise direction when seen from the upper face side of theturntable 301. In addition, in this second embodiment, the projectionangle of the projection lens 12 in the horizontal direction will bedenoted by a projection angle θ_(H) so as to be discriminated from theprojection angle θ used in the first embodiment.

The functional configuration of the projector device 1′ and theconfiguration of an optical system including the projection lens 12 arecommon to the circuit unit and the optical engine unit 110 illustratedin FIG. 4 described above, and thus, description thereof will not bepresented. Here, in the second embodiment, the rotation mechanism unit105 illustrated in FIG. 4 includes the drive unit 313, the protrusion312 a and 312 b described with reference to FIG. 27 and the photointerrupter not illustrated in the figure. The output of the photointerrupter is supplied to the rotation control unit 104 illustrated inFIG. 4. In addition, the motor 320 of the drive unit 313 is driven inaccordance with the drive pulse 122 supplied from the rotation controlunit 104 illustrated in FIG. 4. Furthermore, the rotation control unit104 counts the drive pulses 122, thereby deriving the projection angle θof the projection lens 12 in the horizontal direction.

The operation of the projector device 1′ according to the secondembodiment will be schematically described with reference to theconfiguration illustrated in FIG. 4. Hereinafter, the drum 30 will bedescribed not to rotate in the vertical direction.

For example, image data shaped into a predetermined image size is inputto the projector device 1′ as the input image data 120. Here, it isassumed that the image size of the input image data 120 has a widthlarger than the width of the display element 114. This input image data120 is stored in a memory 101 through an image cut-out unit 100. FIGS.28A, 28B, and 28C schematically illustrate an example of a relationaccording to the second embodiment between the input image data 120stored in the memory 101 and projection image data 331 a, 331 b, and 331c acquired by cutting out the input image data 120 using the imagecut-out unit 100 in accordance with designation performed by the imagecontrol unit 103.

At a projection angle of 0°, the image control unit 103 designates a cutout area of the input image data 120 stored in the memory 101 for theimage cut-out unit 100 based on information of the projection angle θacquired from the rotation control unit 104. For example, at theprojection angle of 0°, the image control unit 103 designates the imagearea 331 a having a width corresponding to the effective display area ofthe display element 114 from a position 2800 located at a left end ofthe input image data 120 as the cut out area for the image cut-out unit100.

The image cut-out unit 100 cuts out the image area 331 a designated asthe cut out area from the input image data 120 stored in the memory 101and outputs the image area 331 a as image data. This image data issupplied to a drive circuit that drives the display element 114 throughan image processing unit 102. The drive circuit drives the displayelement 114 based on the supplied image data. Accordingly, a projectionimage of the image area 331 a is projected to a projection medium suchas a wall or a screen.

For example, when being instructed to change the projection angle θthrough a user operation for the operation unit, the rotation controlunit 104 receives this change instruction through an input control unit119 as a command of a change instruction, generates a drive pulse 122used for driving the motor 320 in accordance with the command of achange instruction, and supplies the generated drive pulse to therotation mechanism unit 105. In the rotation mechanism unit 105, themotor 320 is driven in accordance with the supplied drive pulse 122, andthe turntable 301 is rotated by an angle corresponding to the drivepulse 122.

The drive pulse 122 is supplied from the rotation control unit 104 tothe image control unit 103 as well. The image control unit 103designates a cut out area for the input image data 120 stored in thememory 101 in accordance with the drive pulse 122. Here, in response toa change in the projection angle θ_(H) according to the drive pulse, theimage control unit 103 designates an image area 331 b having a position2801 acquired by moving the image area 331 a by an x₁ pixel in thehorizontal direction as the left end as the cut out area.

The image cut-out unit 100 cuts out the image area 331 b from the inputimage data 120 stored in the memory 101 and outputs the image area 331 bas the image data. This image data is supplied to the drive circuit ofthe display element 114 through the image processing unit 102, wherebythe display element 114 is driven. In this way, for the projectionmedium, the projection image of the image area 331 b is projected to aposition acquired by moving the projection image of the image area 331 aby a change in the projection angle θ_(H).

When being instructed to further change the projection angle θ,similarly, the turntable 301 is rotated by an angle corresponding to thedrive pulse 122 under the control of the rotation control unit 104, andthe projection angle θ_(H) is changed. In addition, in response to achange in the projection angle θ_(H), for example, the image area 331 chaving a position 2802 acquired by further moving the image area 331 bby x₂ pixels in the horizontal direction as the left end is designatedas the cut out area by the image control unit 103. A projection imagethat is based on the image data of this image area 331 c is projected tothe projection medium.

As above, according to the projector device 1′ of the second embodiment,all the input image data 120 having a width larger than the displayelement 114 can be projected while a predetermined area within the inputimage data 120 is moved in the horizontal direction.

Next, a keystone correction performed by the projector device 1′according to this embodiment will be described. FIG. 29 is a diagramthat illustrates the projector device 1′ and major projection directionsof the projection lens 12 according to the second embodiment in a casewhere wall faces 2900 and 2901 are used as the projection faces.

Here, a projection direction 230 represents a direction of a case wherean angle formed by the optical axis of the projection lens 12 of theprojector device 1′ and the wall face 2900 is a right angle, and theprojection angle θ_(H) at this time is defined as 0°. As illustrated inFIG. 29, the projection angle θ of the projection lens 12 of theprojector device 1′ increases to be positive in the counterclockwisedirection in FIG. 29.

A projection direction 2911 is the direction of the boundary between thewall face 2900 and the wall face 2901 that are projection faces lined upto have a predetermined angle therebetween. In the example illustratedin FIG. 29, the predetermined angle is 90°. A projection direction 2910is a projection direction of the projection lens 12 in a case where, ina rectangular projection image that is projected to the wall face 2900so as to be displayed thereon, a left side, which corresponds to thefirst side, of one pair of sides disposed in a direction perpendicularto the horizontal direction that is the movement direction of theprojection image almost coincides with the boundary between the wallface 2900 and the wall face 2901.

A projection direction 2913 is a projection direction of the projectionlens 12 in a case where a right side, which corresponds to the secondside, of the one pair of sides of the projection image of the wall face2901 almost coincides with the boundary between the wall face 2900 andthe wall face 2901. A projection direction 2914 is the direction of thewall face 2901 of the projector device 1′ that horizontally faces towardthe left side, and the optical axis of the projection lens 12 and thewall face 2901 are in the state of crossing each other at the rightangle at this time. The projection angle θ_(H) at this time is 90°.

A boundary storage unit 109 illustrated in FIG. 4 stores the projectionangle at the time of the projection direction 2910 as a boundary startangle, stores the projection angle at the time of a projection direction2911 as a boundary angle, and stores the projection angle at the time ofthe projection direction 2913 as a boundary end angle.

In this embodiment, similarly to the first embodiment, before theprojection of an image relating to a desired content is performed bystarting the projector device 1′, a user performs an initial settingoperation. In this initial setting operation, the user, in a state inwhich a desired zoom magnification at the time of projecting the imagerelating to the desired content is set, rotates the projection directionof the projection lens 12 from the state of the projection direction 230for the wall face 2900 toward the wall face 2901 while projecting animage relating to arbitrary image data.

Then, each time point when the projection direction arrives at theprojection direction 2910 in which the left side, which corresponds tothe first side, of the one pair of sides disposed in the directionperpendicular to the horizontal direction that is the movement directionof the projection image almost coincides with the boundary between thewall face 2900 and the wall face 2901, the projection direction 2913 inwhich the right side, which corresponds to the second side, of the onepair of sides of the projection image almost coincides with the boundarybetween the wall face 2900 and the wall face 2901, and the projectiondirection 2911 in which the optical axis almost coincides with theboundary, when the registration unit 118 receives an event of keypressing according to pressing of a predetermined key using theoperation unit 14 or the like, the projection angles θ_(H) at the timepoints of pressing the key are registered in the boundary storage unit109 as the boundary start angle, the boundary angle, and the boundaryend angle.

A keystone adjustment unit 107 according to this embodiment, similarlyto the first embodiment, sequentially receives current projection anglesθ_(H) from the rotation control unit 104. Then, the keystone adjustmentunit 107, based on the information that is stored in the boundarystorage unit 109, adjusts a correction amount for a trapezoidaldistortion for each of an angle range of the received projection angleθ_(H) of up to the boundary start angle, an angle range from theboundary start angle to the boundary angle, an angle range from theboundary angle to the boundary end angle, and an angle range after theboundary end angle.

A correction coefficient according to this second embodiment is derivedbased on the reciprocal of the ratio between the length of the left sideand the length of the right side of the projection image that isprojected so as to be displayed in a case where a trapezoidal correctionis not performed.

The keystone adjustment unit 107 of the projector device 1′ according tothis second embodiment, for example, until the projection angle θ_(H)arrives at the boundary start angle from 0°, maintains the shape of theprojection image that is projected to the wall face 2900 so as to bedisplayed thereon in an approximate rectangle and accordingly, anadjustment for increasing the correction amount for the trapezoidaldistortion is performed based on the correction coefficient derived inaccordance with the projection angle θ_(H).

Next, the keystone adjustment unit 107 of the projector device 1′, asthe projection angle θ_(H) changes from the boundary start angle to theboundary angle, performs an adjustment for decreasing the correctionamount for the trapezoidal distortion based on the correctioncoefficient derived in accordance with the projection angle θ_(H). Inaddition, the keystone adjustment unit 107, as the projection angleθ_(H) changes from the boundary angle to the boundary end angle,performs an adjustment for increasing the correction amount for thetrapezoidal distortion based on the correction coefficient derived inaccordance with the projection angle θ_(H). In this way, in an anglerange of the projection angle θ_(H) from the boundary start angle to theboundary end angle, the continuity of the shape of the projection imagethat is projected to the wall face so as to be displayed thereon ismaintained.

Then, the keystone adjustment unit 107 of the projector device 1′, asthe projection angle θ_(H) increases to be larger than the boundary endangle, in order to maintain the shape of the projection image that isprojected to the wall face so as to be displayed thereon in anapproximate rectangle again, performs an adjustment for decreasing thecorrection amount for the trapezoidal distortion based on the correctioncoefficient derived in accordance with the projection angle θ_(H).

Here, the keystone adjustment unit 107, similarly to the firstembodiment, determines the projection direction based on the projectionangle θ_(H) and determines a correction direction of a trapezoidalcorrection performed for the trapezoidal distortion based on thedetermination of the projection direction. Here, the correctiondirection represents which one of the left side and the right side ofthe image data is to be compressed. Then, the keystone adjustment unit107 derives each projection angle θ_(H) described above or a correctioncoefficient for the angle range thereof based on the correctiondirection.

The keystone correction unit 108 according to this embodiment correctsthe lengths of the left side and the right side of the image datacorresponding to the left side and the right side of the projectionimage based on the correction coefficient, thereby performing atrapezoidal correction for correcting a trapezoidal distortion of theprojection image.

FIGS. 30A, 30B, and 30C are diagrams that illustrate a trapezoidalcorrection in a case where image data is projected onto the projectionfaces that are the wall faces 2900 and 2901 illustrated in FIG. 29.

FIG. 30A illustrates the shapes of a projection image of a case where atrapezoidal correction is not performed. In FIG. 30A, a shape 3000 isthe shape of the projection image for the projection direction 230, ashape 3001 is the shape of the projection image for the projectiondirection 2910, a shape 3002 is the shape of the projection image forthe projection direction 2911, a shape 3003 is the shape of theprojection image for the projection direction 2913, and a shape 3004 isthe shape of the projection image for the projection direction 2914.Also in a case where the projection image is projected by rotating theprojection lens in the horizontal direction, when the trapezoidalcorrection is not performed, as illustrated in the shapes 3001 and 3003,a trapezoidal distortion occurs in the projection image.

FIG. 30B illustrates an example of the shapes of an image relating tothe image data after the trapezoidal correction. In FIG. 30B, shapes3010, 3011, 3012, 3013, and 3014 illustrate the shapes of the imagerelating to the image data that is a projection target for theprojection directions 230, 2910, 2911, 2913, and 2914 illustrated inFIG. 29.

FIG. 30C illustrates an example of the shapes of projection images thatare projected to the projection medium so as to be displayed thereonbased the image data after the trapezoidal distortion correction isperformed by the keystone correction unit 108. In FIG. 30C, shapes 3020,3021, 3022, 3023, and 3024 illustrate the shapes of the projection imagethat is projected to the projection face so as to be displayed thereonin the projection directions 230, 2910, 2911, 2913, and 2914 illustratedin FIG. 29.

In the case of the projection direction 230, which is in the initialstate, of a projection angle of 0°, as the shape 3010 of an imagerelating to image data, a rectangular shape for which the correctioncoefficient is “1”, in other words, a correction amount for atrapezoidal distortion is zero is formed. Then, on the projection face,the projection image of the shape 3020 that is a rectangle is displayed.

Thereafter, as the projection angle θ_(H) is increased, in order tomaintain the projection image displayed on the projection face to be ina rectangle, the keystone adjustment unit 107 increases the correctionamount for a trapezoidal distortion by gradually decreasing thecorrection coefficient from “1”. In other words, as the projection angleθ_(H) is increased, the trapezoidal shape of the image relating to theimage data is changed such that the length of the left side is furthershorter than the length of the right side.

Then, in a case where the projection angle is in the projectiondirection 2910 corresponding to the boundary start angle at which theleft side of the projection image almost coincides with the boundarybetween the wall face 2900 and the wall face 2901, the shape 3011 of theimage relating to the image data is formed. This shape 3011 has atrapezoidal shape for which the correction amount is largest in an anglerange until the projection angle θ_(H) arrives at the boundary startangle from the initial state, in other words, a trapezoidal shape inwhich a difference between the length of the left side and the length ofthe right side is largest in the range.

Thereafter, the keystone adjustment unit 107 performs an adjustment fordecreasing a correction amount for a trapezoidal distortion, compared tothe case of the shape 3011, by causing the correction coefficient togradually approach “1”, and a trapezoidal correction is performed by thekeystone correction unit 108. In other words, the keystone correctionunit 108 gradually cancels the trapezoidal correction for the image databy decreasing the correction amount by using the keystone adjustmentunit 107 for a trapezoidal correction in the case of the boundary startangle.

Then, in a case where the projection angle θ_(H) is the boundary anglecorresponding to the projection direction 2911, in other words, thedirection of the boundary between the wall face 2900 and the wall face2901, the keystone adjustment unit 107 sets the correction amount for atrapezoidal distortion to zero by setting the correction coefficient to“1” (“−1”), in other words, completely cancels the trapezoidalcorrection for the image data and projects the shape 3012 of an imagerelating to the image data having a rectangular shape again.Accordingly, similarly to the first embodiment described above, whilethe projection image 3022, as illustrated in FIG. 30C, that is theprojection image projected onto the projection medium so as to bedisplayed thereon is not in the shape of a rectangle, the shape can becontinuously changed.

Thereafter, as the projection angle θ_(H) passes through the boundaryangle and is increased, the keystone adjustment unit 107 graduallyincreases the correction amount for a trapezoidal distortion bygradually increasing the correction coefficient from “−1”. In otherwords, in a trapezoidal shape of an image relating to the image data, asthe projection angle θ_(H) increases, the length of the left sidechanges to be longer than the length of the right side. In addition, atthis time, since the correction coefficient is gradually increased from“−1”, the keystone correction unit 108 performs a trapezoidal correctionthat is opposite to the trapezoidal correction used for a projectionimage to be projected to the wall face.

Then, in a case where the projection angle θ_(H) is in the projectiondirection 2913 corresponding to the boundary end angle at which theright side (a side disposed farther from the projector device 1′) of theprojection image almost coincides with the boundary between the wallface 2900 and the wall face 2901, the shape 3013 of the image relatingto the image data is formed. This shape 3013 is a trapezoidal shape forwhich the correction amount is largest in an angle range until theprojection angle θ_(H) arrives at 90° from the boundary end angle, inother words, a trapezoidal shape in which a difference between thelength of the left side and the length of the right side is largest inthe range.

In the way described above, in the angle range in which the projectionangle θ_(H) is larger than the boundary start angle and is smaller thanthe boundary end angle, the shape of the projection image that isprojected to the projection medium so as to be displayed thereon can becontinuously changed.

Then, in a case where the projection angle θ_(H) becomes 90°corresponding to the projection direction 2914, in other words, ahorizontal direction of the projector device 1′ of the wall face 2901, arectangular shape for which the correction coefficient is “1”, in otherwords, the correction amount for a trapezoidal distortion is zero isformed as the shape 3014 of the image relating to the image data. Then,on the projection face, a projection image having the shape 3024 of therectangle is displayed.

In addition, the drum unit including the projection lens 12 may berotated toward the left side, and, as the correction operation, acorrection opposite to the correction of the projection direction 230 tothe projection direction 234 may be performed.

As above, according to this second embodiment, the drum 30 including theprojection lens 12 projects an image while rotating in the horizontaldirection, and, at this time, the keystone adjustment unit 107 and thekeystone correction unit 108 gradually decrease the correction amountfor a trapezoidal distortion when the projection angle θ_(H) of theprojection lens 12 is between the boundary start angle of the projectiondirection at which the left side of the projection image approximatelycoincides with the boundary of the wall face 2900 and the wall face 2901and the boundary angle of the projection direction toward the boundaryand gradually increase the correction amount for a trapezoidaldistortion when the projection angle is between the boundary angle andthe boundary end angle of the projection direction at which the rightside of the projection image approximately coincides with theabove-described boundary. Accordingly, also on the boundary between thetwo projection faces (the wall face 2900 and the wall face 2901), thesmooth and stable projection image that can be easily viewed can bedisplayed.

In addition, the deriving of the correction amount using the keystoneadjustment unit 107 is performed using a technique that is the same asthat of the case of the first embodiment described above.

Modified Example of Second Embodiment

Also in the second embodiment, similarly to the first modified exampleof the first embodiment, the keystone adjustment unit 107 may beconfigured such that the trapezoidal distortion correction is canceledby setting the correction coefficient to “1” or “−1” in a case where theprojection angle θ_(H) becomes an angle near the boundary angle insteadof at a time point when the projection angle θ_(H) becomes precisely theboundary angle.

In addition, also in the second embodiment, similarly to the secondmodified example of the first embodiment, in the initial settingoperation, the registration unit 118 may be configured such that some ofthe boundary start angle, the boundary angle, and the boundary end angleare designated by the user, and the other angles are calculated based onthe designated angles and the view angle α of the projection image.

For example, in the initial setting operation, the registration unit 118may be configured such that the boundary start angle at a time when theleft side of the projection image approximately coincides with theboundary between the wall face 2900 and the wall face 2901 is designatedby the user pressing keys of the operation unit 14, and the boundaryangle having the boundary between the wall face 2900 and the wall face2901 as the projection direction 2911 and the boundary end anglecorresponding to the projection direction 2913 at which the right sideof the projection image approximately coincides with the boundarybetween the wall face 2900 and the wall face 2901 are calculated fromthe boundary start angle by using the view angle α. To the contrary, theregistration unit 118 may be configured such that the boundary end angleis designated by the user, and the boundary start angle is calculatedbased on the boundary end angle and the view angle α.

In addition, in the initial setting operation, the registration unit 118may be configured such that two angles including the boundary startangle and the boundary end angle are designated by the user, and theboundary angle is calculated by using one of the designated angles andthe view angle α.

Alternatively, in the initial setting operation, the registration unit118 may be configured such that only the boundary angle is designated bythe user, and the boundary start angle and the boundary end angle arecalculated by using the boundary angle and the view angle α.

According to the modified example of the second embodiment, the sameadvantages as those of the second embodiment are acquired, and, in theinitial setting operation, all the projection angles θ_(H) of theboundary start angle, the boundary angle, and the boundary end angle donot need to be registered by the user, whereby user convenience isimproved.

Each of the projector devices 1 and 1′ according to the first and secondembodiments and the modified examples thereof has a configuration thatincludes hardware such as a control device such as a central processingunit (CPU), storage devices such as a read only memory (ROM) and arandom access memory (RAM), an HDD, and an operation unit 14.

In addition, the rotation control unit 104, the view angle control unit106, the image control unit 103, the image processing unit 102, theimage cut-out unit 100, the keystone correction unit 108, the keystoneadjustment unit 107, and the registration unit 118 mounted as circuitunits of the projector devices 1 and 1′ of the first and secondembodiments and the modified examples thereof may be configured to berealized by software instead of being configured by hardware.

In a case where the projector device is realized by the software, animage projection program (including an image correction program)executed by the projector devices 1 and 1′ according to the first andsecond embodiments and the modified examples thereof is built in a ROMor the like in advance and is provided as a computer program product.

The image projection program executed by the projector devices 1 and 1′according to the first and second embodiments and the modified examplesthereof may be configured to be recorded on a computer-readablerecording medium such as a compact disk (CD), a flexible disk (FD), or adigital versatile disk (DVD) so as to be provided as a file having aninstallable form or an executable form.

In addition, the image projection program executed by the projectordevices 1 and 1′ according to the first and second embodiments and themodified examples thereof may be configured to be stored in a computerconnected to a network such as the Internet and be provided by beingdownloaded through the network. In addition, the image projectionprogram executed by the projector devices 1 and 1′ according to thefirst and second embodiments and the modified examples thereof may beconfigured to be provided or distributed through a network such as theInternet.

The image projection program executed by the projector devices 1 and 1′according to the first and second embodiments and the modified examplesthereof has a module configuration including the above-described units(the rotation control unit 104, the view angle control unit 106, theimage control unit 103, the image processing unit 102, the image cut-outunit 100, the keystone correction unit 108, the keystone adjustment unit107, the registration unit 118, and the input control unit 119). Asactual hardware, as the CPU reads the image projection program from theROM and executes the read image projection program, the above-describedunits are loaded into a main memory device, and the rotation controlunit 104, the view angle control unit 106, and the image control unit103, the image processing unit 102, the image cut-out unit 100, thekeystone correction unit 108, the keystone adjustment unit 107, theregistration unit 118, and the input control unit 119 are generated onthe main storage device.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A projection device comprising: a projection unitthat converts input image data into light and projects converted lightwith a predetermined view angle as a projection image onto a projectionmedium configured by a first projection face and a second projectionface lined up to have a predetermined angle therebetween; a projectiondirection changing unit that changes a projection direction of theprojection unit from a first projection direction up to a secondprojection direction; a projection angle deriving unit that derives aprojection angle of the projection unit in the projection directionchanged by the projection direction changing unit; and a correction unitthat corrects a trapezoidal distortion of the projection image projectedonto the projection medium in accordance with the projection anglederived by the projection angle deriving unit, wherein the correctionunit sets a correction amount for the trapezoidal distortion of a casewhere the derived projection angle is changed within a range larger thana first predetermined angle determined based on the projection directiontoward a boundary between the first projection face and the secondprojection face and smaller than a second predetermined angle determinedbased on the projection direction toward the boundary to be thecorrection amount for the trapezoidal distortion at one of the firstpredetermined angle and the second predetermined angle or less.
 2. Theprojection device according to claim 1, wherein the correction unitgradually decreases the correction amount for the trapezoidal distortionaccording to a change of the derived projection angle from the firstpredetermined angle to a third predetermined angle that is determinedbased on the projection direction toward the boundary within the rangeand gradually increases the correction amount for the trapezoidaldistortion according to a change of the derived projection angle fromthe third predetermined angle to the second predetermined angle.
 3. Animage correction method comprising: converting input image data intolight and projecting converted light with a predetermined view angle asa projection image onto a projection medium configured by a firstprojection face and a second projection face lined up to have apredetermined angle therebetween using a projection unit; changing aprojection direction of the projection unit from a first projectiondirection up to a second projection direction; deriving a projectionangle of the projection unit in the projection direction changed in thechanging of a projection direction; and correcting a trapezoidaldistortion of the projection image projected onto the projection mediumin accordance with the projection angle derived in the deriving of aprojection angle, wherein, in the correcting of a trapezoidaldistortion, a correction amount for the trapezoidal distortion of a casewhere the derived projection angle is changed within a range larger thana first predetermined angle determined based on the projection directiontoward a boundary between the first projection face and the secondprojection face and smaller than a second predetermined angle determinedbased on the projection direction toward the boundary is set to be thecorrection amount for the trapezoidal distortion at one of the firstpredetermined angle and the second predetermined angle or less.
 4. Theimage correction method according to claim 3, wherein, in the correctingof a trapezoidal distortion, the correction amount for the trapezoidaldistortion according to a change of the derived projection angle fromthe first predetermined angle to a third predetermined angle that isdetermined based on the projection direction toward the boundary withinthe range is gradually decreased, and the correction amount for thetrapezoidal distortion according to a change of the derived projectionangle from the third predetermined angle to the second predeterminedangle is gradually increased.